if only we could seafoam the coolant passages
i prefer the Tomco Klean Screen egr gasket... has a screen to block the larger carbon chunks that might get into the egr and clog it or prevent it from closing all the way.
however... if you got a clogged cat then that might be causing your egr code ... i had a low egr flow or seomthing code when my cat was clogged, makes sense how the code appears when you think about it... skip over your egr code until you check the cat... i really think you are wasting your time thinking something is wrong with the egr/egr tube.
magnaflow has a direct fit cat, cost me like 150-160 (this year) at autozone (just checked and its about 200 now), check all the local parts places then check online for cheaper.
no, can't clean the cat ... but make sure its bad before u replace it. coolant will clog it, eventually. you can unbolt it from the collector, pop out the o2 sensor, see if it runs better. if you have a 0-5psi pressure gauge you can measure backpressure caused by the cat. bang it with a fist to see if it rattles, all else fails drill a hole on either end to visually inspect, think the pipe is too bent to see down it.
i think there is a engine coolant temperature sensor and a separate temperature switch for the fan....
temp sensor/switch might be so clogged with sludge it is too insulated to take a good temperature reading. i dont think you can always count on the A/C compressor to activate the efans, i think it's a pressure switch on the high side that is used to control efans.
i think efan cut-on temp is 220-230ish.