I have a ba xr6t ute with forged pistons and steel rods and it runs around 17psi and when in 1st gear and sometimes 2nd gear if you flatten it, it will rev out really quickly and hits the limiter and for the next 15 or so seconds it will miss and run really bad and if you let the revs drop down to idle it will stall and then takes a wheil to restart like takes heaps of cranking to start. is there bad and is there anyways to fix this? I try not to hit the limiter but because it revs so fast its hard to avoid.

Valve springs

I agree with arronm more than likely valvesprings.

Can someone explain the valve spring theory ?

As in valve float, only happens in the high rpm and will make it go really flat until the springs get back to working again.

The spring weight isnt enough to do there thing when making that extra power and that rpm.

ok so is there any way to tell if they are aftermarket valve springs or standard as I bought the ute with all the mods already done to it. and also when it does start to miss and carry on it like lasts for a fair while and if let to idle and it stalls it takes a lot of winding over for it to fire again like 5 or more times the normal cranking time.

So I understand what valve bounce is, hell I've done it a few times myself before rev limiters were invented.

But how does that make it hard to restart the car?

Lifters pump up during valve bounce, on restart the valves are still partially opening causing hard start

I had new valve springs put in my car in 2010 and last month it started suffering from valve float, so sometimes better springs can break down after some time. My car only tuned to 400 RWHP on 15 psi, going to get atomic springs this time.