"starts to dump fuel"...not following this, you mean the injector pulsewidth increases visually?
The TPS throttle position sensor and the MAP manifold absolute pressure are also key players in a TBI system, as the ECM "looks up" the injector pulsewidth and spark advance from a table based on speed and load. Personally I would change them to eliminate issues and check harness connections.
TBI is very sensitive to vacuum leaks, this could be the gasket under the TBI to any other vacuum lines there are on the motor. It could be the hose going to a PCV valve (not sure if your engine has this) which has a split and is allowing unmetered air to enter the engine.
I would also think about changing the coil. A marginal spark would be a lot more noticeable under load and at speed when the coil is working harder from an electrical standpoint. You could get a "spark plug visualization tool" from Autozone or the like, basically its a set of points that simulate a spark plug. When a HEI ignition is functioning correctly, the spark will jump a 1/2" gap. Don't hold onto the tool while cranking!! If you think about the way the distributor works, there is no mechanical advance, all the advance and retard is done by ECM, so the pole on the rotor is hardly ever going to be pointed directly at the lug for the spark plug wire, inside the distributor cap. The spark must jump that gap to then jump the gap on the plug itself...so if you think about it from that standpoint, the inside of the distributor cap is filled with electrical fire as the engine runs, and the HEI needs a *lot* of energy delivered. This is why I say check and or change the coil.
Also I have to ask about your ignition module, did you change it with the distributor base or is it the same? That's a much lower possibility, in my experience they either run properly or die completely with the engine a no-start-no-run in the latter condition.
The ECM itself is very reliable. I have a 26 year old TBI ECM which functions perfectly in a truck and had a 19-yr old version also in a truck with never a hitch. I have never heard of anyone else having to change one, only at an auto dealership where they didn't really understand what was wrong and "bad computer" seemed like an appropriate diagnosis. Unless the main circuit board was visually corroded or the connectors corroded that would be the last thing I'd change.
