No polution pump!!!! with cat's on ?????????( help)

Hey guys i just pick up my car from the shop
I had a new cluch put in (Center force)
I notice that problem before but now it's geting worse and worse the car has no power it's like somthing holding it back and somtimes i get like back fire if you can call that like 2 or 3 poping sound like someone is shooting i have a 95 mustang Gt 5 speed
I had my polution pump deleted and i have and Mac H pipe with cats that i did not remove is this . Is this a problem no polution pump and i have cats on the car ???????????? Did any body had that problem before????????? should i remove the cats?????????????

Thanks
Derek.N

So that's y my car buck fires and has no power
first thing tomorow my car go to the shop
Thanks i just hope that you are right

Derek.N