5.3 Rough Idle - But No Ecu Code

I have 2000 Tahoe with 5.3 with 63k miles on it. For last 1,000 miles the engine idles rough when warmed up with tranny in drive. BUT NO "CHECK ENGINE" CODE IS TRIGGERED. Twice in last 2 weeks I have had injectors cleaned (at 2 different shops...one a Chevy dealer). The throttle position sensor (TPS) checks out OK. The Idle Air Control Valve above it also checks out OK. The fuel pump was also replaced because of unstable fuel pressure. The rough idle is better now...but NOT totally smooth like it used to be. ??? Again...NO ENGINE CODES TRIGGERED. Any suggestions?

I have a 2001 Tahoe with 39,000 on it that is idling rough as well as it did the same thing around 28,000 on it. The cure was to clean the throttle body air intake butterfly valve.Carbon deposits get on the edge of the butterfly valve allowing too much air and computer has a hard time adjusting for it. Just remove your air intake housing and spray up in there. Don't flood it. The engine may turn over a few times before starting, compensating for all the fluid, but will burn off. Good luck, let me know how you make out.