well i replace all injectors,lower and upper intake gaskets, fixed a ground and set timing to 13 degrees, set fuel to 40 psi...drove ..ran like a raped ape...shut off , restartd idled really low, shut off...started again idled good....repeated idled low, when hitting gas hard it backfired.... why does this thing idle different everytime its started?? tps? ignition module? its on a 90 gt