i have some of mikes parts in my ’89 t3 . cam, cam pulley, custom head (port, polish, oversize stainless valves) and 2 inch exhaust front to rear.
i enjoy the extra pep, my boost is around 10 psi on the gauge (analog)
i have not messed with the vaf- if its working, leave it alone. its hard enough to find parts for the turbo 3 cars .
the oem filter in the oem air box was meant to be blown out and re-used.
a k&n might gum up the vaf, especially if the k&n is over-oiled…
i ran ducting from the bottom oem hole of the airbox, to an open spot in the front bumper-then you could really hear that ihi turbo do its magic
i also had one where the waste-gate was getting hung up- made for crazy boost, but then finally blew out a headgasket…..
when a person starts moving away from oem designs and goes custom , then its a full time job making sure it runs right and doesnt blow up. not saying that the oem designs dont fail, but when you go custom , there are so many things to pay attention to.so many things.
and sometimes, some things just wont work, no matter what you try….