1996 Altima - Need Urgent Help

Friends,

I initially had a P1400 code after lot of testing (which all checked out fine) I assumed it to be a mechanical diaphragm failure inside the EGR solenoid and replace the solenoid. Have driven more than 400 miles and still the EGR system is showing "not ready" but no P1400 code. Meanwhile I am getting P0420 code, for catalytic converter, the exhaust does not smell and the acceleration is good. I do experience a rough idle but the idle is steady at @ 650 rpm- 700rpm will rise higher to @ 850 rpm when the AC compressor or radiator fan comes on. The previous owner stated they had replaced the front O2 sensor, so what could be the problem. The last time I checked the plugs the seemed little while, but that must be due to the EGR malfunctioning leading to the engine running hot.

Anything I need to check before replacing CC. I need to pass emission this week

Thanks in advance........