Engine noise ran fine but had a rough idle?

I got the 2004 C5 at 37k miles and it had aftermarket cam, headers, exhaust, and cold air intake already at purchase. It ran fine but had a rough idle. I took it to a very well respected Tommy Chong to have it tuned. Ran great on non-ethenyl gas but was constantly needing maintenance. Too many to list I had just replaced belt tensioner and idler pulleys and went on a drive and got what sounded like belt of pulley noise again and thought it A/C belt or pulleys, but it wasn't. Took all belts off still the noise. A friend thought it was rocker noise, so I replaced it with up graded rockers still the noise. I took the hearing device with the rod and can't pinpoint the noise it seems to be traveling all through the engine. It sounds just like a bad pulley when standing next to it. I changed and looked at the oil and filter and it was clean, and performance wasn't affected at all. But it's loud and obnoxious. At this point I can't afford to take it to a shop. I would appreciate any thoughts on this.