Hello Diablo, I have a 03, GMC Sierra 2500 4x4 6.0 (GAS) with 56,000 miles. To date I have a K&N CAI and 50 series Flowmasters. Also my 8th postion in my Vin. is a U. I almost bought a super chips programmer but having looked at the Diablo you guys seem to have a few more options as far as custom tunes and Customer service seems to be better( judging by reading the forums ???) MY question to you is this. what kind of numbers can I expect If I want High performance off the line speed with the setup I have already (Low end takeoff is pitiful) and what #'s could I expect with adding shorty headers and MAS also I have to deal with CA smog requirments. Wanting to be loyal customer, convince me! A detailed response would be GREATLY appreciated. thanks in advance.......smitty