I blew the head on my b20 after breaking the timing belt. Now, after installing a b21 head, when i hit the gas it struggles to pick up rpm. Once it hits a certain point it feals fine.It also does that random revving shit. It runs a little bit better when i advance the timing all the way. One thing i didn't do that might have something to do with this is change the intake manifold gasket. ANYBODY please help!