well heres the thing. got a 2nd hand rs efi engine from down southand bought it already out of the car so did not hear it run. spent winter rebuilding everything, and as soon as it started it has a loud ratlle under load and backfires when going downhills in gear. since then ive changed camshaft, hyraluic tappets, cylinder head, injectors, rockers. I had however moved exisiting valves over from last head onto new head as they were in better condition along with valve springs. now thinking the problem must lie here! The strange thing is that when i bought the engine the cylinder head was apperetly recon and i had noticed when stripping that one of the rockers were a golden colour compared to the other 7 grey rockers. could it be that a machine shop has supplied the head to the previous owner with over or undersized valve stem or rocker etc, and could this cause probs if ive got it mixed up? The reason im thinking valve springs is there isnt much else i have now relaced top end and its def to end rattle.