Well can it? And if so would you guys say it could take a large amount of power away?

 

Absolutly! If your exhaust leak is before the O2's it can throw off the O2' readings causing the car to run rich or lean on one or both sides.

 

If you have an exhaust leak at your manifolds or headers it can create false knock and make your car as slow as a riding lawnmower. I remember back in the day in autoshop watching some cheesy video about exhaust systems and how a small exhaust leak could be fatal from the carbon monoxide entering the car and it showed some guys falling asleep from an exhaust leak in a 70's beater car driving off a cliff. Happens all the time! LOL