Shift points and throttle response

Hi, all. I got a (pretty loaded) GLA 250 4Matic last year. I have liked most things about the car, except two things. The throttle response, and the shift points.

Let's start with the shift points, because Mercedes has fixed this. When I got the car, the "E" mode upshifted extremely aggressively. It was not uncommon to be going down the road at 30 MPH in 5th-6th gear at 1000 RPM -- the car was grunting and on the verge of stalling. "S" mode was ridiculous in the other direction -- not at all uncommon to be coasting with little or no throttle input at 50 MPH in 3rd gear with the engine whining between 3500 and 4000 RPM. And it didn't shift into 7th until well after 70 MPH. All in all the two modes were 2-3 gears apart. I deeply craved a middle ground.

I took the car in to service a few months back (Mercedes Benz of San Diego) and they told me everything was "normal". Last week the check engine light lit up, so I took the car to a different dealer (Hoehn Mercedes in Carlsbad). They found a few things -- a few loose pins in the ECU connection, and, most importantly, installed new ECU and TCU programs from Mercedes. What a difference! The car now shifts in "E" less aggressively (when it has about 1500 RPM after the shift) and in "S" a little more aggressively (so the two modes are 1-2 gears apart instead of 2-3). Much more reasonable. Could be tuned a little more, but much better.

Take-home: get thee to the dealer for the ECU/TCU upgrade.

The main issue I am having right now is throttle response. I can do things like take the pedal all the way to the floor and let it go, and there is very little response from the car. Now, I came from an Infiniti G35 which had phenomenal and instantaneous throttle response. I consider any delay to be a safety issue. The real eye opener was when I rented a Ford Focus (the base model, not the ST) in December. 2.0L engine, no turbo. The throttle response was as good as the Infiniti! Instantaneous. Before you could get the pedal to the floor the car was leaping forward. (Oh, and the shift points were exactly where they should have been, to boot. If only the ST came in an automatic, I have knee arthritis and can't do a manual...)

(Oh before anyone asks, I have done the "turn the car on two clicks, hold the pedal down 10 seconds" reset trick. It changed the car from "dangerous" to "drivable".)

I test drove my GLA with one of the Mercedes "senior engineers", and when I demonstrated the "floor it" trick, his response was, "that is anomalous input, of course the computer is going to ignore that". In other words, Mercedes "bakes in" a throttle response delay to see if you "really mean it". I think they are after a "luxurious" rolling start. When the engineer asked if I expected the car to leap forward immediately, I said, "of course, that's what I asked for!" He shook his head and looked at me like I was some sort of alien.

I guess after all that I have two questions:
(1) Is anyone else frustrated by this?
(2) Is there any "tune" that gets around this? In particular, the Carrlson (sp?) and related units modify the input to the ECU but don't change the ECU program itself. And even at full throttle there is a baked-in delay in the ECU programming. So I would need a bona fide ECU reflash. I have not seen this available anywhere.

And... I am very, very interested to see how Infiniti tunes this same engine for the GX30. I think I might have to switch over if it's as good as my G35 was.

Thanks all,
Dan