engine stall

[AD-Denali]

i have a 2006 gmc envoy denali, lifted with Mark's 3" suspension lift, Mark's wheel adapters, BFG's 285/70/17, belsteins in the front and skyjakers in the rear, volant CAI, ATP disconnect, and AP front cv half shafts. everything else is Stock. 90k kilometers on the odometer.

i had a major problem with my tranny a couple of weeks ago and ended up rebuilding the transmission, when i got the vehicle back it seemed like it was stalling/surging when i am on the highway (between 80-100km/h at least i thought) , or wanting to overtake someone slightly it will stall (@ 1400 RPM again atleast i thought), going into corners it also stalls and slows down, all are momentarily until it gives its self a lower gear. the engines idles normally and starts normally.

the stall happens, not on a certain speed, not on a certain RPM, not on a certain gear. however after various scenario testing i found the stall happens with a bog and it seems like wanting to clean its throat sorta of speak when my foot is slightly pressing on the pedal, not past that pedal position and not before

no codes are present whatsoever

things i have done, but the problem remains the same:
replaced spark plug wires
replaced spark plugs
cleaned air filter
cleaned throttle body
replaced speed sensor
calibrated speedometer
changed oil and filters.
removed the CAI and put the stock back
disconnected battery for pcm reset.

after doing a search, it says it might be the EVAP,if it is the EVAP i should get a code or something shouldn't i?

taking it to the dealership and a so called specialized mechanic, they had the following to say:

Dealership: after doing the full service again said the vehicle is running well and there are no issues and dont forget that it is a modified vehicle. WTF if they cannot determine where the problem is, the easiest way out is to blame it on modifications!!!!!.

Independent GMC Mechanic:
is playing the guessing game with me, he says it might be the fuel pump, might be the injectors, and last but not least the transmission turbine

any assistance, incite would be very much appreciated.

[DirtyBacon04]

in the world of helicopter maintanence... this is what we call "F.M." which stands for "////' Magic".

Sorry i have no actual explanation for you, but i can provide comedic relief...

[Trail X]

I'm guessing you have the V8?

[navigator]

if it didn't do it before the tranny work, I would say take it back to the tranny folks.

[AD-Denali]

Yes Sir it is a 5.3 V8

I Was actually suspecting it might Be the transmission and was looking for a confirmation from someone, but knowing the people here I need to have a debate and understand what look for in the trnny.

[The Roadie]

Inconceivable that the dealership couldn't ride around with you demonstrating the problem, using the Tech II to store all data, then looking closely at the frames when the problem happened, looking for intermittent spikes in mixture, throttle plate position, tranny pressures, or something else that correlates to the bogging. That's one of the benefits of a dealer visit to figure out the tough ones.

"modified vehicle" indeed. Suspension mods are not in the cause->effect chain to your symptoms.

[Trail X]

Have you made sure that your trans fluid is at the proper level?

I'm wondering if the 'stall' you're experiencing is shift lag, or slipping in the transmission.

[AD-Denali]

Roadie:
They considered the transmission rebuild a mod since it wasn't done by them,and they don't know what was put into it, they did also consider the lift as having an effect on the transmission and engine alike. The only way that I had them accept it (the car) was by asking them to do a normal service of oilchange and spark plugs and recalibrate the speedometer, that way I would guarantee that they will have to road test it, which they did however without the computer. I already filed a complaint at GM middle east last night. I will wait and see if anyone will repond.

JD:
Yes I did check the tranny fluid and it is normal, I don't think its a slip, because two weeks before I had the slipping and I still remember the feeling.

I was just going through trailvoy site, one thread led me to the other and then to another where I landed onto a cat converter issue, should I also be looking into this or is it a waste of time??