Championship has been thrown wide open after a decision this week by a CAMS Limited judicial hearing.
The hearing in Sydney on Tuesday night excluded championship leader Ric Shaw from the results of the sixth round at Oran Park circuit on 30 July, after stewards found his Mazda RX-7 had used an incorrect differential gear ratio.
Shaw lost the 30 points he had earned for finishing first in two races, was fined $500 and had his racing licence suspended for two months.
He has appealed against the severity of the penalty and CAMS hopes to conduct a further hearing next Wednesday night.
The stewards' decision meant the race wins were re-awarded to Mark King (Mitsubishi Lancer RS Evolution V) and Wayne Boatwright (Subaru Impreza WRX STi), who chalked up the first-ever victory in the series for Subaru.
Shaw, winner of four races over the first four rounds, leads the championship with a reduced tally of 103 points and a margin of only one point over King, who now has won six races.
Depending on the appeal outcome, Shaw may be unable to defend his lead when the seventh of eight rounds is staged on Sunday week at Calder Park, Melbourne.
Craig Denyer, Chief Operating Officer of series organiser PROCAR Australia, said the illegality in Shaw's car was detected as part of an ongoing program to monitor all cars' specifications and performance through the use of compulsory electronic data loggers.
<pre> CHAMPIONSHIP POINTS, after Rd 6 (REVISED): 1. Ric Shaw 103 2. Mark King 102 3. Bob Hughes 59 4. Barry Morcom 51 5. Grant Kenny 46 6. Graham Alexander 45