I have just removed the smog/air pump & the catalytic converter. Under hard acceleration the engine seems to be hesitating & I hear a clicking from behind the speedo in the dash or from the engine compartment driver side. Could this be a problem with the ecm since the pump is now gone, or could it be something else? Thanks!

------------------
1987 Z28 Black & Silver 305 LG4/5-Speed

 

Your smog pump being gone doesn't affect the ECM; mine's been gone for a year & 1/2, and my ECM's fine. With the cat being gone, i'd check/reset your timing, maybe having less backpressure on the engine affected it that much.
Example: friend of mine had an '87 GTA, 350 TPI motor, got it with a zillion mods. Had no cat on it, just a straight pipe. Car always idled crappy and got a little funny on the hi rpms, as soon as he moved out to CA he had to get a cat, after they put it in and he drove away, the car came to life and ran great.
As for the clicking, do you still have the stock exhaust manifolds? Sometimes those manifolds warp or come loose a little and you're actually hearing exhaust "popping" out thru the gap. I've got the same problem on the driver's side in my '84.
Did you remove the aluminum smog tubes that go into the manifolds? If not, you're hearing the check valves on the smog tubes. If this is so, just get some (metal) plumbing caps and put them in place of the check valves.

------------------
DR Stevens
Car #1:
1984 TA L69 H.O.
750 cfm Q-Jet reman. by Holley, 700R4 /w/ Superior shiftkit, 3.42 lim.slip, 4whl disc, underdrive pulleys, Accel HEI, experimental dual snorkel /w/ hood louver, some sort of weird 3" exhaust soon to be replaced
partial emissions delete
Car #2:
'91 Firebird/Formula LO3
K&N air filter Hypertech Thermomaster Chip
more in the near future