[skidlids]

The 4.5mm longer stroke of the ST4 may cause ignition timing issues, but then again the EPROM may have a advance curve that works, hard to tell until its tried.
As for fueling which injectors did the ST4 use was it the green ones, if so a Powercommander should easily be able to sort out the air/fuel ratio.
Only other concern is the TPS as the connector is different but the signal should be OK as the Mathesis can test both