I have a 2003 GMC sierra 5.3l sle. As of recent I replaced the EVAP canister vent valve solenoid, and the EVAP canister purge valve solenoid to try and get my trucks check engine light off. So I replaced both parts and check engine light was off for about 3 days. On the 4th day I was on the interstate going.about 70mph and all of a sudden truck just starts to sputter and hesitate. I wasn't able to continue on the highway due to the sputter and loss of power. So as I limped the truck home on backroads it runs fine when I'm not going.over 45 mph. No check engine light is on so I looked at all the plugs/wires/ignition coils. They were in rough shape. So I replaced all the plugs, wires, and ignition coils. The check engine light came back on when I switched out the EVAP canister vent valve solenoid to the old one, because the truck still ran fine even though the check engine light was on. And went to drive it again to see if it was fixed, it wasn't, and the check engine light came back on and there were 4 codes P0449 confirmed, P0175, P0172, and P0449 pending. I am now stumped as to what the problem is, any help or input would be greatly appreciated. Thanks!