Gentlemen, greetings from across the pond!

I need some help, but first some background

A few years ago I built a TVR Cerbera with an 1999 LS1 and T56 complete with GM ECU, I added a Harrop 112 supercharger, its a great combination weighing just 1070Kg (2300lbs) and made 580bhp at the fly a few years ago. You-tube Supercharged Cerbera, it shows a clean pair of heels to a Ferrari Enzo. (I cant post URL's yet)

I've just got the car back out, new daughter has stopped me playing for the last couple of years!

Just trying to iron out the last small issues and I've hit a brick wall with one of them.

Originally with the TVR engine, the car would pop and bang on the overrun throughout the rev range, sounded great and really was a Cerbera's USP. I've been trying for years to get the LS1 to sound the same, Yes it does pop and bang...... a bit, dual 3" exhaust without CATs helps. DFCO gave the right noise but obviously went quiet once engaged.

I've removed DFCO and added negative timing in the cells where the car is during Decel, this works great below 2300rpm, the car commands negative numbers and pops and bangs BUT...... even if I have -5 deg throughout the rev range, above 2300rpm in decel the car will only command 0 deg no matter what I try, its bugging the hell out of me.

I've captured it in the log below, repeated coast down runs, you can see the 0 deg of timing every time until it hits 2300rpm then it starts to command negative numbers and pops and bangs nicely.

What am I missing guys, thanks in advance

Rich.

Tune and log below.

280317 to work cruise.hpl

280317 final reload.hpt