I have a MY99 Turbo with Green Panel Filter and a TSL GpN back box. Without going to the expense of a remap what is the best way to go next for a bit of power gain. Is a decat downpipe the next step - or the mid section. Want to keep one cat just in case of MOT issues preferably. What bhp gain, or what sort of "feel" would the next step provide? Advice appreciated!

 

get the center section replaced

 

DeCat downpipe dropped boost threshold on my 97UK by about 200rpm and smoothed out low-speed/ high-gear driveability. I kept the oe centre-section and never had any probs with the MOT.

You might want to consider fitting a dawes device if you're after a bit more performance, but I'd include a boost gauge as well so you can keep an eye out for boost spikes etc.

Next mods for me would be porting the headers and fitting a samco y-piece. After that you're looking at mapping to get the most out of the hardware.