Hi, im chasing a few more KW from my non turbo rb30, shy of bolting another turbo to it im not exactly sure how to go about tuning a non turbo motor. Do things like 3" throttle bodys, larger induction pipes, tuned exhausts, and fancy spark plugs actually make a difference? or am I looking at $1000+ in parts for less gains than a solar panel. At the moment ive done most of the basics, RB30 bottom end RB25DE 10.5:1 pistons VCT r33 RB25 Head shaved flat 3-4 times previously Front facing ebay 'freddy' intake plenum Uprated fuel system, ethanol compatible Nitrous oxcide I guess the next steps are Clean up the inside of the intake plenum, (pitted cast alloy) Larger throatle body Uprated ignition? (used to blow out spark at 20+psi) 2.5" exhaust? 2.75" 3"? Port matching? ---------- Post added 30-09-13 at 12:14 ---------- The other thing that annoys me about this engine is that with a GT35/40 1.06 rear used to build an exceptional amount of power from 4000rpm, full boost at 4500rpm and it would be all be over by 5200rpm Is that a sign that the cams need upgrading, previous head on pull down was found to be leaking 'mach 10 spec' across 20 valves. Is this a sign of too many revs, too softer valve springs or too much hp? And another question, does load seem to effect boost for you as much as me? in first gear you would be lucky to see 5psi, on a dyno 12-14psi, and yet 4th gear it will shoot past 20psi and hold between 4500-5500rpm before droping back to around 16psi at 7500-8000prm (5psi wastegate spring and bleed valve.)