FWIW, i used 5 star to tune my ecoboost explorer. They did about 6 revisions where i'd load a tune, datalog a few pulls and send it back. After they revised and sent it back to me, i'd repeat the process. I'm very happy with the tune and the gains, but their customer service was a little lacking, Response times to any email was 2-3 days at least. If i called, they'd tell me they'd relay the message to whoever, and it was another few days before they called back. They did say repeatedly that they were super busy and backed up, but i dont know if it was the truth or just an excuse. In the end, i got what i paid for and was happy with the results. Of course, a naturally aspirated engine is going to be limited in what kind of gains you can actually make, but they can tweak the transmission and throttle response (if its drive by wire) and make huge improvements to drivability.
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