Ok let me give you the past history, 1998 honda civic lx 176,000 miles.. it died on me while driving about 3 weeks ago. Before that time the check engine line had been on for 2 years.. thats right 2 years.. had the 02 sensors replaced summer '08.. thought that was it.. had cracked manifold soldered spring 2010.. had control module and coil replaced 8-10.. as well as new tuneup w/ngk plugs.. then diag threw a 02 sensor code.. replaced it.. mechanic thought that was problem.. now car is throwing a 420 catalytic converter code.. mechanic said all is fine unless emissions comes back. 2nd day after having it back car was having a problem getting up a hill and a ramp to xpressway..
My theory is that it is the catalytic converter clogged and Im going tomorrow to have the sucker cut off!! Anybody else with any knowledge of this??

Here was my last suggestion:

P0420--Catalyst System Efficiency Below Threshold. It may not be blocked but it may be seriously compromised. You will likely have to replace the converter.

After replacing the converter, you likely won't have any more problems.

Without a good catalytic converter, your Civic won't run properly.