I work @ a dealer where we got a 98 z with long tube headers, highflow cats, thunder racing MAF, NOS, air box, msd rev limiter, 4:10 gears, hurst shifter and this is only what is visible. It runs excellent but idles rough and has some valvetrain clicking at idle. Could this be aftermarket rockers, springs that cause this or do ls1 motors need valve adjustments? I Know this motor has been run hard. The car looks to have been meticulously maintained and put together right. I have a 96ws6 that is tired @128000 and needs work. The z has caught my attention but i don't want to trade one prob for another. I have no knowledge of ls1 motors other than some 98's having oil probs.