T25 on KA-T making noise and not reaching full boost! Help!

[ShimiBoi]

Hello all,

First off, thank you all for your help in advance. So I just turbo'd my KA with SR piping and a T25. I recently replaced the hose going to the wastegate from the intake piping (between the IC and TB) with a much longer hose that is about a foot longer to accommodate a MBC. However, I decided not to connect it but left the hose long. Now I have noticed that there is a weird noise coming from the turbo under boost and a whistle when slowing down in neutral, which never used to happen. Motor slightly bogs down then idles at 700rpm (normal was 900rpm). AFR is still mid 15s at idle. Boost gauge needle shakes between 6 - 7psi in 3rd gear at WOT. Turbo no good? Wastegate opening? Sorry for the long post. Please help.