I did have them on my Mk5 GTI. APR tuned to Stage 2+ but the seal that the piston slides inside failed allowing fuel into my oil. The stepped design of the piston places extra pressure on the seal that it's not designed for. And of course you cant buy just the seal, or even just the part that the seal is in. You have to buy a whole new fuel pump.
So I replaced the Autotech internals with Integrated Engineering internals which come with the part that holds the seal along with a correspondingly larger seal for their internals.
Granted, my car did already have 130ish thousand k's on it when I installed the Autotech internals and in hindsight I think it was already starting to fail, but none the less I wouldn't get them again.
There is are thread on here about them causing this failure. I'll see if I can find it. A quick google search for autotech fuel pump upgrade failure should yield the results you're looking for.