check all of your vacuum lines, usually they crack. change out the intake manifold o-rings.
http://home.everestkc.net/richyrich/then check all coil connections. check ohm resisitance all plug wires, which have a resistor in the plug connection, which could go bad.
first thing I would check is the vacuum diaphragm of the OEM petcock. search my posts for part #s and installing a snubber in the vacuum line. If its crack/worn near the center it is not fully opening causing low fuel flow look with magnification or u might not see the wear.