So... I'm not sure how to explain the stumble...
Let's say I'm merging onto the highway in 3rd, I floor it because I want moar powah baby. Then instead of feeling the engine power/boost, I get this stumble. It will stumble between 3k and 4k rpm and then stops stumbling as it accelerates.
Sometimes I wonder if it's a boost issue. However, I also wonder if it's fuel pump issue (sometimes when I put my key to ON and you expect the fuel to pressurize, I hear what can only be described as a small whale/dolphin making a low volume mating call off in the distance -- car starts and runs seemingly fine). edit: I should add that if it's cold and if I accelerate up a hill at very low RPM it will surge like no tomorrow.
TYPE OF STUTTER/STUMBLE
Steady throttle/Increasing throttle/Both: both
MODS
Intake: stock
Exhaust: stock
Fuel: 91 pump - no noticeable change on 94 pump
Turbo: stock - td04hla
Engine Management: stock -- own a tactrix v2
Tuner and revision of tune(if you don't mind): none
MAINTENANCE
Sensors changed: none
Plugs changed: 1 step colder iridium
Coil Packs changed: none
OTHER SYMPTOMS
Check Engine Light: nope
Etc: -
RESULTS
What has and hasn't worked for you: changed to colder plugs and may have reduced stumble slightly... however, still there
If something worked, how long has it been working for: -