I've got my '90 TurboII with the following:
Cone Filter
Custom 2.5" full exhaust (crinkle-wall), no cats (they were clogged - nobody from the EPA here is there?).
Mechanical boost gauge

That's about all that'll deal with boost.

It doesn't run the full ~8 lbs boost it's supposed to, something electric I think is messed up.. BUT..

In 1st it runs right to 5.5lbs ok
In 2nd it runs to 5.5lbs ok also
In 3rd it runs to maybe 6 lbs and stays
In 4th on the freeway it goes immediately to like 7.5 lbs and stays there, doesn't creep though
In 5th, maybe like 6.5 or 7 lbs again (I haven't had it at like 6k in 5th gear though).

Anyone know why it runs immediately up to 7.5 in 4th, but won't do that in any other gear at all? It's stopping RIGHT at 5.5lbs before, where the wastegate is mechanically sprung. It's really really odd.. and I don't think it's creeping, which is odd.

 

The S5's have an electronic boost control up by the oil filler neck. Do you still have it? just get a MBC and pitch the factory one.

 

yeah that's why I think it's not boosting right, either the DSV is messed up (I tested it and it worked fine though), or the wiring to the DSV is messed up (maybe) or the wiring from the pressure sensor to the ECU might be messed up (maybe). I was just curious as to why it'll jump RIGHT to 7.5psi only in 4th though, it was weird.

 

8psi its supposed to? you mean with the mods you got?

 

I would think it would run straight to 8 psi in at least 3rd, instead of the about 6 psi it runs to now.

 

ya stock you should get 8 in all gears.

if the boost controller isn't working you'll get 5.5. since that is what the spring is set at.

 

so no reason why I go 5.5, 5.5, 6, 8 without ANY creep?

 

your boost controler probabably isn't working and you are cheaping to 8?

run a vac line right from the turbo to wastegate and see if it still goes to 8

 

I have a hard enough time SEEING the lines, let alone getting in there to skip over the DSV. I'll just leave it be.. besides, it's frigging SNOWING up here in Michigan. But it's not back home in Cleveland, I'm moving back.