98 Vortec 5.7 "multiple misfire" code

[gchemist]

A neighber has a 98 Vortec 5.7 "multiple misfire"- code on his truck. The plugs, wires, distributor, rotor, fuel filter and coil have all been changed. The problem still exists. It seems when we unplugged the IAT sensor (right past the air cleaner) the engine responded right away. $8.99 and the problem still exists through all RPM ranges. If the sensor is bad will it give a code? Unplugged the coolant sensor just try it to.
There seems to be an overflow of fuel in the TB. Could it be a bad fuel pressure regulator? How can you trouble shoot it? It seems that the problem is now mechanical in nature. Everything else checks out.
Hey is there software available to ODBII diagnosis? Anything that can be used with a laptop and port connector?


What is the fuel pressure for the engine? Anyone else solve a smiliar problem?