Any ideas as to what would cause fuel pressure at the rail to not hold one second, and then two minute later stay up? New fuel pump, no codes, fuses good, car will start but idles rough, and strong smell (unspent fuel?) coming from exhaust, again it would seem something in the fuel delivery/injectors is out of whack. If fuel pressure was normal, I'd suspect optispark, but with pressure holding, then not holding, then holding again, I'm not sure. Car was running perfect last week, then died and has not been right since. It's a 94 6 spd lt1 68K miles. Thanks.