i am stumped as to why after doing a Lower intake gasket and upper plenum that now my exhaust is plugged and my cat gets cherry red hot. any thoughts or suggestions?

 

Knock too much carbon loose?

Maybe just a coincidence

 

To much coolant blew through exhaust before the repair was done to clog the cat is my guess.

 

I was very careful doing the work, I cleaned the intake and throttle body off the car. There was no white smoke indicating a burning coolant condition... just a strong sulfer odor about a min or two after startup... I didn't rev the motor at start either, I let it naturally catch up with the idle and run for a few min to warmup to burp the cooling system then as I checked my gauges I smelled the odor in the car and faint smoke coming up from the console area... then the check engine light came on followed by a backfire after massaging the throttle, I shut it down and looked under the car and I seen a cherry red cat... that's all the details I got.... now last week I had the tranny done for a P1811 update kit however the car ran flawless prior to the intake job I did.