this is not APRs fault at all, before you go bashing them understand how a turbo works. Simply as the lower altitude the more air the more HP the engine puts out no matter if you're tuned or not. The higher altitude the less air the worse ANY turbo will run, not just an APR tuned car. I have a friend that has a GTR and when we go up into the mountains there cars slow down because its how turbos work just like how they run a hell alot better in cold rather in the hot. so please dont blame APR and if you dont like it thats why they have a 30 day money back guarantee
Having nothing to do with APR (yet) there are additional variables for tuning at high elevation. It is a matter, in combination, of timing, psi/rpm profiling, fueling, AF ratio, and even on this car, potentially barometric pressure. The thin air provides more challenges than just "air" being moved. It is O2 content, compression, humidity (or lack thereof at higher elevations), fuel grade, turbo RPM, etc.
Here in Denver, one can see just about ANY pre-production VAG car (VW, Audi, Porsche, Lambo, Bentley, Bugatti) test mules driving around the city as well as in the mountains, up-to and including Mt. Evans (at 14k feet). Why do you think OEMs do that testing here?
Some tuners take time to test their software at higher elevations, others don't. Plain and simple. I have had multiple tunes on a number of VAG cars I have owned, and some companies were responsive to looking at data logs, others weren't (and continue to not be). I have tested for a couple of companies with pre-production files...and I can tell you definitively who I never tested for (or anyone else I know, and it is a LOT of VAG folks)...Additionally, the OP's complaint is NOT unique among customers in Denver, and we are only at 5280 ft (see above).
It is not about the car slowing down, it is about it running correctly. My OEM tune is certainly a bit slower than sea-level, but it doesn't have a hiccup to be found.
