Rep Power: 670

So I've noticed in the last two weeks that I've lost some horsepower in my car. Not sure why, I just past 100,000km last night.Only mods are a magnaflow catback and new rims and tires. Any input would be great.

 
Rep Power: 878

What do you mean by lost horsepower? documented or you just feel slugish? Any codes poping up? Last time of tune-up?

Exhaust restrictive? Cat could be clogged, just throwing something common out there since you havnt described to us too much.

 
Rep Power: 670

The car feels slugish.The cat is 5 months old,but I've never had a tune up.And I've put 13,000km on the car since i bought it in november

 
Rep Power: 603

try the spark pugls and wires and air fuilter

 
Rep Power: 878

Yes If you never did a tune up it is about time to do so since you havnt allready, not knowing if the last owner kept up on it doesnt give you a good idea of what your working work. A basic tune up of plugs, wires, all filters, pvc etc etc. all the somewhat cheap maintenance will help out any engine. Do that and then see where your at from there.