No aftermarket parts, port modifications, or other variations from stock configuration are allowed. (en.wikipedia.org)
This makes it more than a match for FX - 57 systems, which have a single core and a 2.8 - GHz stock configuration speed. (pcmag.com)
The rules were along the same lines as the European Group A specifications, rather than the showroom stock configuration of the series from 1985 through 1989. (world-challenge.com)