New DSM owner, fuel cut question

[Quattro18t]

Hey all my name is Joe. I own a 99.5 audi a4 1.8t quattro 5 speed for my weekend driver/ mod car. I just bought a 1991 Talon TSI AWD with 30K on rebuild motor, and 25K on transmission. It has the following mods: spec stage 3 clutch
buschur racing ported axhaust manifold
HKS 50mm external wastegate
2.5 inch slowmo o2 housing
3 in mandrel bent exhaust w/cutout
2 in megan racing lowering springs
kyb GR-2 struts up front
kyb AGX struts in the rear
factory wheels painted gunmetal

It is my daily driver for now and I have a question about fuel cut I am experiencing. Whenever I gun it, boost will kick in around 3500-4k rpms and spikes up to 15psi sometimes (wastegate creeps past stock boost), around 5500rpms I will hit fuel cut and the car will surge until I let off the gas. I know the wastegate is too large for the stock turbo but is there any spring I can purchase for it to make it not spike such high boost or would I be better off going back to a stock wastegate?

 

[Quattro18t]

Is there a big crack in the wastegate plumbing? Or is that a shadow from something?

No, its just the shadow. Im pretty positive its a boost leak. I will check out the flapper this weekend when I have a chance. And yes the car is pretty hacked up but the previous owner bought it as a shell and basically rebuilt the whole car. Runs perfect but when I hit boost it def. sounds like theres a leak somewhere under the hood. Thanks for all the help, I will let you guys know what I find.

 

[JusMX141]

Runs perfect but when I hit boost it def. sounds like theres a leak somewhere under the hood.

Well if your gate is externally dumped, there IS a leak somewhere under the hood when you hit boost!