Catted X-pipe Install Sluggish Acceleration 1 Week After

I have a 1995 Mustang gt 165,000 miles. Anyways I had a catted x-pipe installed last week it removed 2 out of 4 catalytic converters check engine light is on. Today I drove it to get a haircut it drove fine. Then got back in the car and drove 5 miles back to school and the car was being sluggish with acceleration. Like it would accelerate up to 2,000 rpm but not go past it and stay at the same speed and then pressing to pedal down more it would go past this after a few seconds (basically it was like the acceleration was delayed). This is the first/only time its done this this week.

I'm thinking since it removed 2 of the 4 cats and put the check engine light on it is messing with the cars performance now maybe?

Anybody else have problems related to this?

The old o2 sensors were plugged in to the new x pipe. And it's like the car is losing power and not accelerating at all and lagging when driving. It also was shaking a bit at idle and sometimes the idle has sounded inconsistent front the tailpipe. I'm taking it back to the same mechanic in a few days I will also try to dump codes or have them do it