boost problems

01a4 1.8t when I start to go sometimes only sometimes will I get full boost and rip thru 1-3 gear but the rest of the time half or less got motor rebuilt replaced all gaskets and hoses and vac lines. I didn't remember to get a boost gauge and ran out of money. But there is a noise that's got me baffled when I push on gas turbo spools u can hear the psshh when changing gears but it almost always it psssh's (DV) when I ride a gear and don't want to change gears or it pssh's right before I change gears too. Is the DV bad or is it my N75 or both please gimme y'alls opinion. Thanks









P.s bout forgot when I'm riding and I gas it to high rpm's it will psshh and like thump or pop sound?