inlet cam rattles badly!!!

[stonersgsi16v]

bin having alot of problems with my pre ecotec gsi, wont idle and replaced icv and tps etc just wont tick over smooth now iv got a rattle on the inlet cam from 1500 to limiter revs fine above 1500 rpm and sounds like a misfire below 1500rpm, could the caps be loose on the inlet cam? had one put in out of a tigra 1.6 bout a month ago? cheers