BOGGING at 3800-4000 switch over ?! been doing for abit now, mainly in 5th, but fitted de-cat as its 19yr old, its 'better' but still there, if double tap the gas then it can some times pull though, getting annoying now ... any one fixed this problem? searched alot about but no joy

Mod's as it stands - 3" turbo back japspeed to HKS back box.
HKS airfilters ... thats all engine mod's. thanks in advance.

 

anyone ??

 

have you looked at your charge control valve? it may not be functioning properly

 

Try checking all your ground connection

 

Not sure if you're already figured it out but in addition to what rexy91 said about checking your grounds, adjust your timing (via CAS) and then calibrate your TPS.