I've had RocketChip on my 99.5 Jetta since 140,000 miles... about to cross 300,000 now In that car the chip affects fuel, boost, and timing. The only worry I'd have when getting a reliable chip tune is wearing out the automatic trans faster.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.