So, shop diagnosed problem I was having with various CEL lights after going over severe road bumps like rail road tracks as battery ground cable that goes from battery to starter as shorted. Apparently, the previous shop did a poor job of installing long tube headers. They didn't move cable so the heat from the LT melted the battery cable insulation. Secondly, they didn't clock the connection at the starter so when the insulation melted the exposed cable was too close to the metal heat shield of the starter so a severe bump would cause the heat shield to shake and cause the exposed cable to short. The recommendation of the new shop after consultation with the GM dealership was to replace the 3 vehicle computers and of course replace the ground wire. After the repair I now have a weird problem. After the vehicle sits for a prolonged time (over night or after a 9 hour work shift) when I turn the key I get a reduced engine power message, a service stabillitrak CEL, the gas pedal is not responsive, and if I put transmission in gear the truck will only idle around. If I wait 30 secs or sometimes as long a couple of minutes the truck will fire up with no warning messages or CEL. A check with a primitive hand held scanner reveals 2 codes related to the long tube headers. Does anyone have any idea of a fix? The only difference since the new shop touched the truck is new computers, new battery cable, and new tune. I think one shop uses EFI live to tune and the other use HP tuners. Wonder if the malfunction is a possible theft deterrent function of my original key and the new computer or a "no hack' gremlin left behind in the tune from original shop. Thanks in advance of your reply.