2001 S-10 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