So the VTEC did engage/switch before the cluster swap? I can't remember for sure if that car has the VSS that reads off the tranny or not. It was '90 that the prelude switched to that, since the new civic came out for '92 model year, I'd guess your '91 is the older setup... It's not going to engage as you've found out unless the ECU knows that it's traveling above 13 or so mph. Is it the '91 trans. you're running or did it come w/ the engine?