Aftermarket units have a lot of weight removed; reducing idle RPM energy too much. This requires throttle-up to get get going or engine quits. The Z32 is V engine with a small crankshaft. It doesn't have as much rotational energy as an in-line 6. Typically I like to remove what is commonly known as the inertial ring. In the Z32 it is a belly close to the ring gear. In Hondas I have never re-balanced after removing material with the surfacing grinder. In the Z32 that belly has to be cut down using a lathe. Those I have re-balanced with the pressure plate on. Loosing 4 to 6 makes wonders for the feel of the engine.
