I cut the cats up front out and also th elarge middle cat......There was a metel pipe going from the middle cat to some where on top of the motor. What is that and should i cap it out front. I gonna by the air pump removal kit ...but what should i do fornow thanks......Its a stock 91

 

The pipe is the downstream air injection into the catalyst bed from your air pump.

 

I understand that but should i seal it or leave iopen uptop?

 

It needs to be sealed if don't want exhaust leaks.

 

thanks