Re: Why is my car lacking high rpm grunt?
Well to tell you the truth - your crazy the standard injectors can not pump enough fuel into your motor at those boost levels. You are basically asking for a piston through the firewall with the standard injectors with that boost!!
I have 10spi and make 256rwkw at 4900rpm and above that it runs dangerously lean and could detontate. I need more fuel to make more power any higher than that. If your running 13psi then you nuts, or ignorant!
I would either get a more conservative tune (like I am) or purchase the necessart hardware to help maintain such boost levels. You'll need injectors, and definately valve springs. The surging is your valve springs bouncing under the increased load.
If its any consellation - my valve springs are on their limit now with only 10psi and thats above average.
Once you get enough fuel into the motor start thinking about a new exhaust and you'll make the same power with much less boost, and then you'll have to think about heat soak and less restrictive intake tract, but now your talking post 300rwkw. Many thousands to go past that. For your case, anouth $1500 ought to fix it all up.
256rwkw @ 1920kgs