Sounds like you have found the problem. I have not had any experience with the direct fit cats, but I have used magnaflow universal cats before. Just have to cut and weld with those.

 

Yeah I think so. Direct fit is just easier for me since I'm unable to weld.

Any thoughts on the needing gas to start sometimes?

 

Just an update. Couldn't get the cat off myself so in the end had to take it to a friend's shop. Turns out almost everything from the cat back was stopped up really good and corroded inside. One new cat and muffler later, and the blazer now runs smoothly. Hopefully that is the end of my woes! Kinda curious though what would make almost the entire system go bad like that?

 

this is an interesting tread! i think my cat is plugged too. i couldnt remove the cat so i started smashing the honeycomb material inside the cat from the back of it with a long fork and hammer. broke it all up but not all of it came out. but atleast it can breathe now. ill have to find a way to remove the cat from the truck to get out the rest....

 

shop vac.

 

I'm not a mechanic, I know minimal about FI, but what i do know is what my brother pounded into my head back with my olds that had the same problem, had to give it gas to start and since it's Feul injected, i shouldn't of had to do that. He told me

"Check the fuel rails and injecters. If they are bad, they don't work and you have to pump the gas, if they are good you wouldn't have to pump the gas."

But thinking about it, my mom had the same kind of problem with her Lumina, she had to hold the gas pedal down slightly to start it, so my guess on the fuel thing would be check your fuel system out, injectors, rails, maybe even fuel pump, anything that is on the motor that sends fuel into the motor.
Something is either block by gunk or it is failing completely. Now, when my moms car did this, it didn't give out a code for it, it was all basically trial and error, hit and miss kind of thing when diagnosing it. Takes time and patience.

All I had to do with my olds achieva was dump some of that lucas injector cleaner into it, seemed to fix the problem with a couple of fill ups.

 

if you have to hold down your gas pedal to start it, that could also indicate you need more air because you have a leaking FPR or leaking poppets that are creating an overly rich condition.....