of course you have the ko4 turbo, cant do the settings as I dont have a sps, one thing I dont do is use asda fuel, optimax all the way but like you say I should set it up for this fuel, I know what you mean about tailing off as mine does this so possible the stage 2 will
help the top end a little bit and will be more catered for the mods I have.
I got my supersprint cat back for 330 quid but dont know how much it is for a full system, millteks hi flow cat is 350+ but unsure if that is with the turbo down pipe?
Might have to take a trip to my nearest revo dealer which is now bristol I think as TSR are no longer trading, maybe they will do some setting for the fuel