I have a 2000 silverado 5.3l 4wd auto. Im pulling a dtc p0405 imedeiately after resetting and stays on and a p0300 every once in a long while. I assume the misfire code was because of the egr. Truck was running fine, till i decided to replace the egr valve, now it is unresponsive and putters when tring to accelerate on the highway, only when i throttle down and drop to a passing gear i get a response without a puttering, shaking or loping. It doesnt seems to be the tranny at all it runs and drives great. I do have a diablo perfomance tune with the cats tuned out. Im really not sure which route to go with this problem bc financialy i cant replace everything i read it could be. Any advice on where i should be looking to fix this problem. I here the pcm goes out when the egr vavle goes, is there any truth to that?