[gchemist]

96 and later GM vehicles for sure. Anything older I'm not so sure. You are better off by calling. They get swampped with work sometimes. With fuel prices through the roof, I'm sure he is getting a lot work right now.
I'll keep posting updates. Next week, I'll get a chance to drive 200 miles at 70 MPG. My average speed in city driving is 35 to 45 MPH. A little freeway now and then too. Lights fortunately are spread out too. Block to block traffic lights are uncommon unless I drive downtown.
Oh, note that I'm driving 29" 255/60R17 wheels too. The tires raised the Jimmy nearly 2"!