I had second thoughts about takeing the cats off of my truck, so I put a new set of magnaflow cats on, and it feels like crap. The truck doesnt want to move. Any suggestions? Also it down shifts for the smallest inclines, any ideas why? Any info. will help

 

I now have a magnaflow 14" muffler. But dont want the truck to be too loud. Would it be wise to take the cats off again and leave it at that or would it be better to leave them on and try to get the sensors to work.