The Opel Vectras run in DTM against Mercedes CLKs and Audi TTs. BMW doesn't run in the series.

Anyway, just remember that horsepower is a calculation of torque so the two are always related. You can trade high-end torque for low-end torque and that's it. The way you make more power is to make more revs or to make more torque (at any point in the rev band). Yes, in effect if you increase the low-end torque of a motor you will decrease its high-end horsepower. Once again, and I can't say it enough, THIS IS BECAUSE HORSEPOWER IS A CALCULATION OF TORQUE AND RPM.