truck starts and runs good with no misses.. then after about 30 to 45 seconds starts idling rough.. rev it up and no miss but at idle rough idle?

was going to clean throttle body but saw a guy selling a bbk 75 mm tb on another board and bought it...so will clean it when that arrives..

any ideas on what would make it rough idle after about 30-45 secs?

 

Do a search on IAC [idle air controler]. Try cleaning it, if that makes it worse replace it.