I have a 87 turbo. Everytime I boost it creeps to 16 psi. I knew it was the wastegate. so today I went to my friends house picked up a series 5 turbine housing and manafold, which has a bigger wastegate to stop boost creep. It fixed the problem and feels alot faster and spools at the drop of a dime, I don't like that though if you go over 3000 rpm it pins you. Before with the series 4 the profec A wouldn't work it knew there was a problem, a very smart piece. Now it works fine. the turbines are the same but I sware at 10 psi with the series 5 turbo it feels faster than 16 psi with the series 4.

 

bump

 

A lot of people just port the wastegate themselves, but I don't kow how many people know that the s5 turbo is a direct bolt on, and gives a great performance boost!
Not to mention the bigger wastegate.

 

and it sound tough as ****. way louder. I love it.

 

I have heard the 87-88 turbo has a .88 AR and the 89+ has 1.0 AR. That would make it less of a restriction and help power. Glad it worked out so well; I have one ready to go in on the rebuild for my 87.