Hello. First timer here. Old timer everywhere else!

2010 with 142K. Vehicle was working perfectly and the check engine light came on. Code was P0401. EGR valve and gaskets. I bought the kit from PartsGeek. My mechanic changed it but didnt do the other steps, ie; cleaning cooler, pipes, intake manifold etc... I drove a few miles and my gas pedal went limp, car knocked a few times as I turned into a pkg lot and turned off the engine. I did start it again and made it home, 14 miles.
I've been reading, watching and researching and I told mechanic about after market parts being not read by the ECM and cleaning the carbons from the system ....he took the plug off of old EGR and put it on new one....that fixed the ECM deal. Now my mechanic wants to clean my cats!!!! Wth? Would that even help? Shouldn't he clean the parts of the EGR system FIRST? I bought 4 cans of the stuff that is safe for aluminum and plastic.....and I have already paid quite handsomely for the repair in the first place.
Im in Phoenix if anyone has a good, trustworthy mechanic in the area.
Thank you for any response. Be well.