REDLINE

...I add a bonez hi- flow cat? Right now, I've got an HKS DP stock everything else and am boosting 10 psi. When I added an HKS cat-back, I got 10 psi still, except it spooled up faster. (I'm planning on putting the stock cat-back back on after I get the hi-flow.)

GsrSol

I would say 11psi at most, it's still a cat and restrictive but it flows a little better then the stock cat. It's nothing to worry about.

Mahjik

iTrader: (1)

You might see 11 PSI. I really didn't notice a change in my boost pattern until I upgraded my ECU.

kevinmfaust

Your major restriction is now the intake. Add a cat back and a high flow intake and you will not be able to keep boost down. I think most people are finding that cold air intake, down pipe, and a cat back is all that the stock waste gate will manage. When a high flow cat is installed people are having to open the waste gate ports.
Kevin

Toadman

Without the stock cat back on, you'd be toeing the edge of motor martyrdom without an ECU.

widebody2

I had cat back, dp, and cold air intake for a few days...4th gear would spike to 15 lbs once in a while...not a good thing on stock ecu. besides the spikes I was getting like 11 or 12

REDLINE

I talked to Jeff at Rotary Power (rotary shop here in L.A.) he says, as long as I keep my stock cat-back and stock intake, the most I'll be boosting is 11 psi. Does this sound right? Like I said, when I added the DP, I didn't notice a change in boost level...only spooling speed. The same went for the stock cat-back vs. HKS....only thing affected was spooling time.

Mahjik

iTrader: (1)

Yep, pretty much like my situation. I didn't see any spiking when I added my hi-flo. When you get to the ECU upgrade, that's when you'll really see a difference.