How can I be so sure??

 

Those are typical codes thrown for clogged CATS. No real good way to check for sure other than pulling them off. You would see a big temp difference in the pipe before and after the cat but risk engine damage running it.

 

If you have a infered temp gun you can test befor the cat and after. It should be hotter after the cat, But as Kysilverado said you can hurt the engine more by getting it up to temp to test. You can also remove the cat and see if that helps.

 

So all u diagnose as this as the cats!!!

 

Will this cause a truck not to idle too?

 

easy (well...not exactly) test is unhook the cats from the headers (open headers) and see if the truck starts to act better. tie up the system to you can drive it and go down the street. this will show if it IS the cats or not....

 

if yo udo not have headers just take out the 02 sensors in the front of the cat and see what happens are you can also drop the pipes off the manifolds.

 

Would the cats plugging cause a overheating problem while towing as well?

 

go put your hand over the tail pipe like i said before,that will tell the tail.or even better unhook the exhaust just behind the cat's and see how much its flowing there.

 

i had the same prob on my 03 s10,it wouldnt go over 20mph at wot