My 1987 K5 is having a throttle issue. The motor (350 TBI) is new only 1500 miles on motor. Motor has a lunati. 454 cam, long tube headers, and a holly 670 throttle body with a 2" spacer. Motor was installed about about 2 months ago. Truck idles great but when sitting at a stop then hit the gas to go the truck boggs down when I let off the gas a little bit the truck will go just fine. The truck does not have the power that one would expect. Any help would be greatly appreciated .