crxerebuni

i bought 91 zc crx.it had a vtech engine(sir i think) in it with other owner.it was replaced with zc.so i have it.ive put a D16A9 engine into it with L3 gearbox.i have to change front engine mount as it wont sit right. the L.E.D picked up a few problems but we sorted them.there are no faults now.But the engine isnt running right.its over fuelling and running rich through all revs.
Now, with the old zc the cat light was flickering.(i didnt think a zc had a cat,was it the one left in it from the sir engine??)i have it in the garage, they reckon to put a cat on it would solve my problem?any ideas?are there any wiring mods to be done with this swap?i thought it was meant to be a straight swap?thanks everyone