Chevy 350 weak

Alright recently i rebuilt my motor. I got the cam turned, new bearings and rings. New rods and lifters too. Also 10:1 compression pistons. I put everything together and my neighbor torqued it all but it ends up that he forgot to torque the intake manifold. Anyways we got the motor together and running and i raced it against a iroc z28, torched his car by 4 buslengths. It was the best the car ever ran. Afterwords i put new spark plugs and wires in too to gain more power but i noticed a sever oil leak. I realized the intake manifold was loose so i tightened them and now i have less power! I can barley spin the tires now. I am assuming that the car was getting so much air from the leak and the air fuel ratio was perfect therefore running great. Once i closed that leak i am thinking i am getting too much gas or not enough air. All i know is the plugs are sometimes wet with gas. Also my left head was smoking gas fumes so i installed a pcv system and stopped that. My timing is usually good to. Is it that i am getting too much gas or air, i installed a fuel pressure regulator and set it at 5.5 like the carb. manual says. What could be the problem!?

Remove the intake and replace the gaskets. When you retorked it you broke the seal on a couple of intake runners. Torque from the midle out in a criss-cross pattern. Of courde, jmho