Ever since I got the ARD Blue tune my car has had a weird hesitation, plus it 'bucks' hard just beyond 4100 RPM in 4th gear (which kinda sucks, that's the sweet spot for passing someone). Aside from the hesitiation, which I've gotten used to, it'll pull hard w/ no issues all the way to the rev limiter in 1st, 2nd, and 3rd gear; but once I hit 4th gear at around 4100 RPM it starts bucking badly (it actually broke the motor mount once). If I upshift into 5th when it starts bucking, its fine; or so I thought. The other day I took it up to 100 for the first time (on a closed track of coarse) and noticed it won't rev beyond 4100 RPM in 5th or 6th gear either.
Seems very odd to me that 1st, 2nd and 3rd gears are fine but 4th, 5th and 6th are problematic. 4th gear is the worst one, if I don't shift prior the 4100 RPM it'll buck hard, basically it goes from WOT to zero pull for a split second (almost like the key got shut off), then back to WOT again; but if I leave it floored in 4th gear it'll keep doing this. Its pretty much done this since I got the trans and the tune done last Dec, I obviously don't drive my car 100mph so I didn't realize 5th and 6th were also included. 5th and 6th gear doesn't necessarily 'buck' like 4th gear does, its more of like its hitting a rev limiter in those gears.
When this happens, my boost isn't doing anything odd (until it bucks, then it drops quick and pulls again during the buck). I don't have a CEL either.
Any suggestions???