Hi, I'm new to the forum. I have a 97 K1500 w/350 V8. Rebuilt my engine with some mods and took it to get power tuned at a dyno shop. It seems the 96 & 97 Chev trucks don't have a user friendly computer as far as compatibility to readily available programs. I think I may have that problem solved but..... when I power run the truck in third gear (Automatic) it upshifts to lockup at 3500 rpm or around eighty mph. It does this whether or not I have the shift selector in 3rd or OD. I drove a 96 and it behaves the same way. It seems the shift is regulated by speed(?) regardless of the throttle position. When it upshifts... I not realizing my peak on the power curve and the truck kinda falls flat on it's face because of the upshift at only 3500 rpm. I'm going to try another program to change the 3rd gear shift point but wonder if doing that will prevent my overdrive from working like it's supposed to during normal driving for the sake of gas mileage. Any advice would be deeply appreciated. Thanks, Big AL