I was digging around under my '01 Maxima SE AE today taking a closer look at my y-pipe. My question are:

There are two stock pre-cats. It appears that the aftermarket y-pipes (Cattman, Stillen, ...) only replace the second pre-cat. Is this true of all of the aftermarket y-pipes? I believe so, but I just want some confirmation.

Secondly, if this is indeed the case, has anyone removed the first precat and installed a "straight pipe" in it's place? To do this you'd have to be creative with the flanges and also tapering a pipe down to the right diameter.

Lastly, I was wanting to remove my first precat to take a look into the exhaust manifold, but was unsuccessful. I removed all of the heat shields and bolts (5 up top, 3 below) but couldn't break it loose? Any advice on how to remove it?

Thanks for the help.

 

Well.. both the Y pipes out remove the first precat. As far as I know if you want remove it... you gotta replace your ypipe. As far as removing the bolts... bigger wrence.. more leverage?

 

I saw a pic of Y2KevSE's Stillen pipe and it appears that it does NOT remove the front pre-cat. It stops at the 3 bolt flange before making the turn up to the exhaust manifold. I have yet to see a pic of the 5th gen Cattman y-pipe, so I'm not sure if it's the same way or not.

As far as the bigger wrench goes, I successfully removed all of the bolts, but still can't break the cat free. I'm going to go yank on it some more right now.

 

Maybe thats a difference between cali spec and other y-pipes?

 

That is the difference. On fed emission cars the front pre-cat is in a different location and the emission standards are different, not as stringent. So removing the front pre-cat doesn't cause ECU errors.
Beware though, on CA/NLEV emission maximas if you remove the front pre-cat you will cause the ECU to complain invoking the "check engine" condition. I would not recommend removing it.