2000 Jimmy, 4.3L ignition coil, dis. cap, rotor button, plugs and wires are all less than 6 months old. I started having problems starting early mornings when frost hits. I just put in a new starter and battery. I feel it's a fuel issue, but scan is only showing P0453 (high tank pressure) and occasionally P0452 (low tank pressure). Both are EVAP errors indicating to me that the pressure in the fuel tank is inconsistent. I've recently been hearing a gurgling noise under the fuel plenum, and need to cycle the key numerous times to build up pressure in the system before it will start. Then once it fires up the gurgling noise stops. Even if I turn it off and start cycling the key again, the noise wont come back until it sits for a while (at least very faint). Once its been running, it will start up time and time again until it sits overnight again. it idles a little rough, but no misfires are indicated on the scan. I'm thinking that possibly it's a problem with the fuel pressure regulator not holding the pressure and causing the fuel to trace back into the tank. My question is, is it possible that it could be my fuel pump itself, and any idea why the regulator would only fail on cold mornings? It seems I can try to start at 5 degrees and it wont start (Cranks fine), I can come back to it an hour later at 7 degrees and it fires right up first try without even cycling the key. Could the bad regulator have fowled my plugs that fast that the cold weather is causing them not to fire? With winter coming I'm hoping to wrap up this issue this week and any insight would be appreciated. thanks.