Check that MAF

[LS1-450]

Car running rich or sluggish in general. Check the inlet side of the small resistors (sensors) on your MAF. Especially those using high flow air filters.
If they are covered w/ crud because of an under oiled filter, loose filter connection, or oil from an over oiled filter, they will not properly sense the volume of incoming air. This can cause the car to run rich @ low rpm or sluggish in general. If dirty, clean very carefully with a q-tip. Be careful not to damage those tiny wires. More than once, I have found this to be the cause of a performance issue.

It's a good idea to check once every six months or more.

[Sarge]

Good advice and accurate....some use brake cleaner...I use electrical component cleaner from Radio Shack....cleans them lil boogers good!

[5150]

just cleaned my this weekend with brake cleaner, was kinda dirty seems to run better now.

[GatorSS]

Electrical component cleaner works best.