2001 s10 4.3 4x4 no power and stumbles

just recently replaced intake gaskets cause well you know did fpr cam crank and manifold sensors while i was in there also replaced timming chain and gears cap and rotor new o2s and cat. now the truck has no power off idle till i hit full throttle vacuum reads 16in steady fuel pressure with just key on is about 57psi and doesnt drop after key off while engine is running pressure reads around 50-52 psi if i throttle up the pressure rises to 57-58psi im getting p0300 code good ole random miss fire just looking for advice