They'll be lots of replies I'm sure but it depends on budget really. S3 (bargain s/h if you can find one),THS or as you've said Airtec. I know that the THS is better for high HP (400+) cars than the S3 for instance. The S3 is absolutely fine for probably up to 380hp from what I've learnt and been told.
I'm no expert, I just took my tuners advice and mine has been absolutely fine on numerous track days in all weather conditions. Mine's stage 2+. No heat-soak or power loss.
Hope this is of some use to you.
