I have an 89 TBI that i replaced the cat back on and replaced the damaged cat with a pipe. The exhaust leak is coming from the passenger side up near the manifold, but I cannot figure out where from.

The previous owner removed some tubing from the A.I.R. pump leading from the black box to the metal tube that runs behind the engine to the cat.

With the engine running I can stick my hand up by the Y pipe to manifold connected on the passenger side and feel some air, but I don't know from where. Its really loud when running and I can hear clicking as well. Pretty annoying.

 

Probably a bad connection at where the y pipe meets the manifold. Take it apart to inspect it, I like to smear some antiseize on the connection, under the flange, & on the tightening surfaces. It helps let the y pipe slide on better, tighten flange bolts evenly too. Sometimes smacking the flange in 3 places with a long punch helps.