hey guys i live in australia and need some advice on what mods to do to my ls1 before i get an after market computer any advice would be great there are a lot of blokes in aus that do work on ls1's but they tell you confilcting info they are just after a dollar cheers

 

LT's, Cat back, Lid, P+P'd TB first of all... Good gains to be had there. You can have the stock ECM tuned to fit the modifications done. THen go w/ an LS6 intake if you don't have one already. What year is the car?

Then after the EXH is done, then look into a rear or gears.. Then you can dive into the engine w heads and cam. Depending on what you want the car to do.

What are your HP goals? AutoX? 1/4 mile? Do the suspension also, it'll help you get more out of what you have.

 

You may get more responses in the 'gen III external engine' section. The stickys at the top in that section have a lot of good info for what you're interested in:
https://ls1tech.com/forums/generation-iii-external-engine/520845-mod-guide-induction-exhaust-please-read-before-posting.html

 

cheers mate i have short stroke struts and shocks over sized twin piston calipers slotted rotors 3.9 diff gears and 2 1/2 inch cat back twin system modified air intake not sure what manifold ?holden de-tuned the ls1 like crazy is it any better to put aftermarket ignition set up on. Any what advice on size headers to put on ? i wouldn't mind stroking it to a 383 but inexprience have me stuck there!