2003 wagon hesitation
Hi! This is my first post on the site, though I have lurked around for awhile. I know that the topic of hesitation has many posts, and I have tried to get as much as I can from these before posting my own. However, I've been troubleshooting this problem for awhile, and I can't seem to figure it out. My car is a 2003 wrx wagon, stock except for a cat back exhaust. 95k miles.
The issue that I am having is hesitation under load above 3500 rpms or so. In first gear, the car feels good and pulls hard above 4500. The car seems to pull fairly well in 2nd gear as well, no hesitation; it doesn't pull quite as hard as in first though. In 3rd, I seem to get good turbo spool at partial throttle up until about 3500 or so. Above 3500, at partial or WOT, I get hesitation all the way to the end of the tach. Same deal in forth and fifth; car feels good until I get over 3500. The hesitation isn't violent, it just slightly jerks through the tach and doesn't pull very hard.
I don't have a boost gauge or wideband, so I have no troubleshooting tools now. Here is what I have done:
replace spark plugs (stock Pt plugs, gapped to 0.030)
check for vacuum leaks (I'm about 90% sure there aren't any)
checked all intake connections
put fuel system cleaner into current tank
disconnect front O2 sensor (hesitation still present)
disconnect MAF (car died)
stock air filter (about 7k miles on it)
Sorry for the long post, but I would appreciate any input that you guys can give.