P 0507 Engine Code/intake replacement

Hello,

I helped a friend with his 1998 Lesabre 3.8. We just replaced the notorious upper intake plenum and the car seems to run fine. After driving for a couple hours and maybe 60 miles the check engine light came on with the P 0507 code. Something about the engines RPM's are higher than what is required for the current engine operation. Does this seem like a throttle position sensor??

Any help would be much appreciated. Thanks,

Brehmster

The computer is commanding a a mcertain idle speed but the engine is idling higher the the pcm is trying to maintain, dirty iac, slight vacuum leak, improperly set base idle, you get the idea.