bit of a story but thanks in advance for taking the time to help. 89 z32 tt jap import went from stock with exhaust making 240whp and running perfectly. to 740cc injectors, twin pod filters maf delete, Mac valve (ebcs) 14psi, ait sensor, link g4+, God speed smics making just shy of 350whp. the problem i have is intermittent but I'm pretty sure it's only when the engine is warm. problem is I have a rattle that's at 1000rpm and above. also when I depress the throttle in neutral the revs go down to 400rpm then go up. while driving when I clutch in the revs drop right down to 400rpm then settle out at 800rpm and idle. I'm thinking maybe something is worn after being hammered on the dyno? when the rattle isn't there the car idles and runs like a bloody dream oil is changed every 2000ks I was running 5w40 oil for the last year. if just changed to 10w40 thinking it might quiet down the noise bit it didn't make a difference. has anyone experienced something like this? how do I go about diagnosing the problem without opening the engine?