Stock car reads around low to mid 130's on our mustang if I remember correctly. It's been a long time since we actually had a stock car on there. My car is back to stock for a short time for some NA parts testing so I'll get a base run if you guys care to see what a stock car makes on our mustang :P The Dyno Dynamics down at HG Motorsports we were using for awhile also reads mid 130's for a stock FR-S, BRZ. It's not uncommon for a Dyno Dynamics, Mustang, Maha, just a matter of whether you're running it in true heartbreaker mode or any sort of sim mode. We always prefer the lowest, truest reading and it looks like you do too @
nelsmar 
Sincerely,
Zach
Delicious Tuning