i have a obd1 2.9 TB bored out, with bigger butterfly. i compared it wit std 2.8 obd1 and it was bout 3mm bigger. it did make a difference, but not much better than my other one which had the lumps removed? think i was just expecting a bigger difference. throttle response is loads better and picks up better. on flywheel subject do u lose any top end with the lighten fly wheel? i know RS turbos did, i had one lighten and it had a shit top speed? maybe took to much off??