2004 Cadillac SRX Question: Can a bad electronic throttle control unit cause damage to cadillac converters?

I took my cadillac to the shop because i was having problems with the engine stumbling and losing power. they replaced the electronic throttle unit (throttle body assembly) and the MAF sensors as well as a new EFI fuel injector. 14 days later my car has the same problem and now theyre stating that the damaged throttle body has caused the caddilac converters to crap out. Is that statement reasonable or are they just trying to milk us for money? please help! Thanks in advance