For which car? Bluefin is generally known to be a milder tune than the others but it also $300-400 cheaper so its relative to cost. I had a Bluefin stage 1 tune on my Mk6 Golf R and it was fine - gave a dyno verified 20kw at the wheels gain (went from 166kw to 186kw). On the stage 1 tune the car ran perfectly fine, no issues at all.
Not long after that, i decided i wanted more power, so i installed an aftermarket downpipe and intake and got a stage 2 tune from Bluefin. Car was not happy, was running very rich (could smell it and see it coming out the back) and my fuel consumption was noticeably worse even with sedate city driving. Went back and forth with Bluefin (very good customer service) and tried several revisions of the tune with little to no difference. I decided to try another tuner (DNA Tuning) for their stage 2 tune and instantly the car was back to normal behavior and with a nice gain in power (once again dyno verified at 204kw). I eventually went stage 3 with DNA Tuning and power went to 211kw.
Seeing you are in Melbourne i would seriously recommend you chat to the guys at Underground Performance Underground Performance
I am now researching a tune for my wifes SQ5 and am considering Bluefin again - but with this car there are not many options available.
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