04 or 04.5

Which criteria is used for finding out? Do they go by the serial # or by the date of manufacture? If so, what serial # is the cutoff? Or if by the date, what is the cutoff date? Does this really matter in our discussions or are we just getting picky? If so, where does it come into play?
Thanks
FLo

 

I have an '04. If it was manufactured before January 1, 2004 it is an 04. After January 1, it is an 04.5. The 04 has no cat and is 305/555. The 04.5 has a cat and is 320/600 if I remember correctly.

 

Thanks Z06,
I'll have to check the date on mine since I am not sure now.
Have to check to see if I have a cat too. I don't really recall seeing one while I was crawling under, just saw a huge muffler and 4" pipe.
Are those the only differences? Why the power difference between the 04 and 04.5? I thought I've read on this (and other forums) that removing the cat won't buy you anymore power of fuel economy since the cat only has a 0.5psi pressure drop across it... and no one so far noticed any benefits and/or improvements after removing the culprit.
Thanks again

 

It is not the cat that adds the power, that was just an add on for emission garbage. I don't have a cat on mine because first off, I don't care for cats, more of a dog person. And secondly, it is unneeded extra weight

pop your hood, look on the driver's side of the engine. There is a plate there that will either say 305/555 or 325/600.

 

thanks again, I'll do that.
F

 

Ok, it is 04.5.
Looks like I have something that resembles a resonator there instead of the cat. What does or did your cat look like? This one is a spun unit which has the shape of a cylinder with a cone at each end. It is welded in rather than clamped in. Would that be a cat, or an after-market resonator someone had installed ?
F

 

The 04.5 is also when the went to the electronic control waste gate too isn't it?

 

yup, I think thats when we went from boost elbows to boost foolers.......

 

thats is a cat you got the 04.5 and up also have a 4'' exhaust were the 04 has 3.5