2002 Denali low RPM's

When at idle it seems like the truck sometimes wants to idle under 1000 rpm's also when I make a slow turn, the truck seems like it looses power at lower idle!

Any advise where too start?

I recentally had a tune-up done, new wires, plugs, pcv, air, fuel filter! I never cleaned the IAC and throttle yet! What is the resistance for the TPS?

Thanx