my 90 t2 is stock right now except for cone filter.....and i want some extra power, what can i do without touching the stock fuel system (pump, injectors), is it safe to do exhaust?

 

Exhaust might be okay, shouldnt cause too much creep, especially with the S5 turbo.

 

For what it's worth...... I run a couple of turbo cars that have the Mazdatrix 2 1/2 downpipe and presilencers with on of the two with a DynoMax catback (the other stock catback) and a wideband monitor for looking at the afr, and I have no problems. Stock injectors. Stock fuel pump (I did do the so called fuel pump re-wire for something to do one day). It's been a couple of years on one car and about a year on the other. The afr reads rich at full throttle and the down side is that with the 2 1/2 inch piping I don't see over 10 psi.

If you go to the full three inch piping .......you've got to do something about several items...fuel pump, injectors etc.

Oh....both engines fully rebuilt by yours truly so I can drive out of state and not worry about what the clown that owned the car prior to me did to abuse the engine.

I elected to go with the 2 1/2 for several reasons, one of which is reliability. But hey, I'm a turbo newbie, wadda I know?