Stock boost levels are 7psi and 11.8 psi.

The car has a factory boost controller called the t/vsv.

When conditions are correct, the t/vsv opens and let's the boost increase to 11.8psi.

Conditions being it not being freezing outside, the car is up to operating temperature, no knock has been detected.

The stock fuel cut is at 12.8psi.

I'd bet you wouldn't get much more than 13 or 14psi with that exhaust on there and I'd be curious to delete the fuel cut to see how far it creeps.

Make sure the car is in tip top condition with refreshed ignition components and a fuel filter.

Run on 99+ octane.

What I'm about to explain removes your fuel cut entirely.

If you understand that, there is no need to fear.

Pull the boost pressure sensor hose out of the bottom of the boost pressure sensor

(next to the diagnostic box) and block the hose up with a small bolt.

Now take the car out somewhere quiet where you can test it in 3rd and 4th under load.

Take off and accelerate.

Move into 3rd and go WOT and keep an eye on your boost gauge.

If it passes 15psi, back off.

My bet is it won't though, I think it will settle at 14psi, maybe 15psi at most.

That is a

'safe' level as long as you aren't beating om the car around a circuit or driving in 30 degree heat and beating on the car.

If it climbs over 15psi and keeps going.

You have a car that boost creeps and good luck to you solving it.
