I have a 91 Trans Am, LB9 with 131,000 miles on it. I'm having a slight stumbling problem that has developed over the last 2-3 weeks. I've been perusing the boards and have seen it mentioned that my catalytic converter could be causing this problem.

Tonight, on a whim, I took my K&N out and knocked some of the crud off it, re-oiled it and as I went to put it back I realized something. The canister the filter sits in (with the 3" snout on it) sits on a base that is large enough to support the filter. It had a drain hole of some sort, so I blocked that with a bolt and 2 nuts (for safety) and bolted the top and filter right onto the base.

I realize this isn't any type of CAI, but it felt better (SOTP) especially in the midrange.

But I digress, the stumble was still present only after the system goes into closed loop. I presume I should feel the stumble constantly if the cat. was plugged?

Ignition is about a year old, consisting of a bosch cap, rotor and 8mm wire set, running on platinum +4s. Other than the filter I have done the throttle body coolant bypass mod. Nothing else. I am still running the original exhaust. I recently did a fuel filter change, but do not have the means to check fuel pressure to see if that could be causing the problem. Soon to be rectified. I can't remember if I changed the O2 sensor in this one ot the last one (old age) but could swear I did change the EGR valve on this one just after I bought it. (within the last 3 years)

The engine pulls very strong, even though the original 2.73 rearend is still in it, I turn consistant 15.5's in the 1/4.

I have seen a slight amount of moisture near the water inlet where the intake manifold hits the heads, so I may be developing an intake manifold leak, but other than that I can see no problems. Any suggestions?

TIA