I've got one for ya! I own a 90 that had / has a nosey top end (CLACK!) I replace the lifters-pushronds- guideplates-rockers-springs and had the heads done and also replaced the injecters, STILL nosey! I thought it might be the lifter retainers smacking the block but I've heard other 90's that don't clack and some that do. I do know that it is coming from the valley ( strong clacking from intake area) and the injector sound is different. Any help on this one???