My tuner once said he had a customer that ran 600's in his 33gtr on a standard ecu. They dyno'd it with the 600's and it was a little on the rich but thought it would be ok, 2weeks later the aftermarket computer arrived they checked the tune again with the standard ecu and it ran near perfect mixtures everywhere. In saying that it would be advisable to check the state of tune before going to silly with it. Ryan