was there ever questions about the computer chips he was running in his Sierras which apparently gave them all of the horsepower?
I don't think so.
I think Dick Johnson's problem in '87 was getting hold of the computer which reprogrammed the chips.
Andy Rouse was the Sierra guru of the time and wouldn't sell them.
Johnson eventually found the computer he needed in the States and was smoking all the European Sierras by Silverstone in '88.
The next year top British Sierra runners (Rob Gravett) were buying cars from Dick...
So I don't think he was cheating, just dogged engineering!
Legend has it Johnson's Sierra had 680hp during its pole run at its final appearance at Bathurst in '92.
Look at the massive clouds of smoke as he changes gear up mountain straight..!