06 evo ix, while building boost it feels like the car is being dragged down. just had the car tuned by a reputable shop a few weeks back and the car ran like a raped ape, but eventually this problem aroused. also it sounds as if the wastegate were to be stuck open, making a loud whooshing noise while in boost. problem is at its worst in 4th & 5th gear. changed turbo, wastegate, and BOV with known good parts, still has the same problem, and is building boost.

hks intake, stock manifold, stock turbo, +1 oversized valves, stock cams, 3'' turbo back exhaust, L19 head studs, exedy twin clutch, stock intercooler, walbro 255, gates T/B nothing too extreme.

 

Maybe a boost leak. Check your intercooler piping for Ang loose connections. I'd start there. Here's a link for a great company's product for testing your car for boost leaks. This is seriously the cheapest and fastest way I've found to test your car for boost leaks. What rpm is this happening at? And is it only in 4-5th gear? Here's the link: http://www.turboboostleaktesters.com...16G/Categories

 

What is this please? Also, what BOV, or diverter are you running? AnabolicEVO is right. Do a boost leak test as he sugsests.

 

Figure the more info the better. Basically trying to say as much info as possible to hopefully get better replies. I have already done a boost leak and she passed. I had the oem BOV and tried a agency power POS. same problem is still there in all gears just at its worst in 4th-5th