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So, i bought my 2018 gla 45 on 25 jan from carmax. i thought it had been modded and questioned the sales and service people there. they assured me it was not. the car had great power and acceleration.



while doing paperwork on the sale, i asked for a copy of the title. i contacted the previous owner by snail mail. he called me about 3 weeks later and told me he had put a renntech tune and downpipe on it. it ran great, so i really did not care too much. I told carmax and they said not to worry, they later said they contacted the dealer and they said they would still cover it.



however, i got a CEL for p0420 in early march. it went out before i could get it to the dealer. i got the code again 2 weeks ago. i took it to the dealer and now, of course, they discovered it is modded and they will not cover.



today, carmax says they will pay mercedes to convert back to stock. my problem is that i bought the car based on the way it drove with those mods. I love the car, but don't see it as being nearly as powerful.



The big question is, do i keep it unmodded and less powerful, or get them to buy it back for my same purchase price and taxes??? I'm not sure how much of a battle that will be.
 

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I guess it goes back to how much do you love the car. The Renntech tune and downpipe probably go you to about 400-410hp from 375. The big difference you will witness is the change in torque with the ECU tune. The car still feels fast even at stock and I believe you will enjoy it but if that isn't what you bought then go with the refund. I enjoyed mine before the tune and after the tune. Plus you have the option to a piggyback if you want and take it off when you go get it serviced.
 

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Would you be be able to drive it once the tune is removed, before you make your decision? I would guess that you'll still be very happy with the performance. I'm sure you'll notice a difference, but it should still be pretty close. Otherwise, I'd say if you have the option to piggy-back the the tune so you can add and remove it before dealer visits, that seems like a decent option.
 

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Piggy back tunes are still detectable by the dealer. P0420 is a bad cat or 02 sensor. Does the down pipe even have a cat? If not, that is your issue. You can choose to ignore the code, which the previous owner obviously did, or have a highflow cat installed. They aren't that expensive.
 

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Find a dealer with a stock 45 you can drive. That will give you a good side by side comparison.
 

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So, i bought my 2018 gla 45 on 25 jan from carmax. i thought it had been modded and questioned the sales and service people there. they assured me it was not. the car had great power and acceleration.



while doing paperwork on the sale, i asked for a copy of the title. i contacted the previous owner by snail mail. he called me about 3 weeks later and told me he had put a renntech tune and downpipe on it. it ran great, so i really did not care too much. I told carmax and they said not to worry, they later said they contacted the dealer and they said they would still cover it.



however, i got a CEL for p0420 in early march. it went out before i could get it to the dealer. i got the code again 2 weeks ago. i took it to the dealer and now, of course, they discovered it is modded and they will not cover.



today, carmax says they will pay mercedes to convert back to stock. my problem is that i bought the car based on the way it drove with those mods. I love the car, but don't see it as being nearly as powerful.



The big question is, do i keep it unmodded and less powerful, or get them to buy it back for my same purchase price and taxes??? I'm not sure how much of a battle that will be.
you are lucky you got those parts ready to go. value of 3-4k if you are go by them new plus installations.
DP from renntech comes with 200cel , so you ll need to instal spacer bellow.
it has 3 sizes,
Run the mid size jet. If you get the P013b again, run the biggest one. If you get the P0420 , run the smallest.---- ( notes from my tech)

or drive it as is. i have same set up with 200cel and light still comes on ones in awhile, it usually takes a couple of day to light turn off.

but i would not bother with the engine light drive it as is. and get cheap scan tool for piece of mind to make sure what coeds come on.
c

https://www.jegs.com/i/Vibrant+Perfo...4aAk_0EALw_wcB
 

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Discussion Starter #7
thanks for all the feedback. PO sent me a dyno sheet that shows 360 hp and 390 ft lbs torque. so, it runs great. Carmax is saying that if I don't like it after going to stock, we can discuss other options.



Caug, the link didn't work. was it a link to the spacers? do you still get an occasional CEL with it installed? Any idea what might set it off? Mine did reset itself both times after a week or so.



Nevada has annual emission testing so it has to work. With my luck, it won't work when i have to have it tested. lol. My old audi has been heavily modded and i never had CELs until i moved here and had to have it tested.
 

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I bet you will not like the car as much if you undo the mods. GLA45 is great. 375 HP is great. I love mine. But it can't compare to my F80 M3. You will notice the drop in power and torque if you undo. I notice the difference every time I switch between them.

The mod you got in the car is good stuff. I would keep them. But if you worry about future warranty, even if you switch back, the dealers already know your car has been modded. Not sure if they will cover it again ever.
 

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Discussion Starter #10
so, i decided to swap back. I dropped it off this morning and picked it up this afternoon. Def a different car. it does not have the snaps and farts it had. Acceleration is ok from start, but big diff when you step on it around 50. It used to snap you back not so much anymore.



renntech really had it dialed in...the way it should have come from the factory.



i'll drive it some more, but def not the same as before. ):
 
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