OK how bout a fun one.....my 04 silverado has a strange rpm lag in the 4k range at full punch...it sometimes even drops back a few rpm's then goes on up. Sometimes a quick slap of the pedal will get it jumpin right on up...I added a K & N air intake set up and then a Hypertech tuner program (87 octane) and still have the lag..actually a bit worse... it has done this since day one, well actually after about 5k 'cause I didn't get into it to notice this......any suggestions?

take it to the dealer and let them worry about it. Don't try to fix something covered under warranty.

Check your MAF for oil from the K&N filter. If it is dirty, you should use electronic cleaner (Radio Shack) to clean it.

The other thing to check is fuel pressure. If possible, check it while the problem occurs (I have taped the gauge to the windshield) and make sure it is not dropping off then the problem occurs. It is a good idea to have a friend come along to read the gauge so you can keep your eyes on the road.

//2000CAYukon