Y-pipe Install with Stock Pre-cat
 

I have had three plastic cross-over pipes crack/break and so I am going with the E-fini Y-pipe install. My car still has a pre-cat. Has anyone successfully installed a Y-pipe with the pre-cat without removing, or, lowering the pre-cat first? If so, I would appreciate any tips. I am struggling with the nuts that hold the rear airway in place.

Welcome to the world of doing it yourself. This nut is a pain in the ass, but if you contort yourself enough you can get it off. I have done it about 100 times, and it sucks each time. The easiest way I ever did this was from under the car with about 4 ratchet extensions end to end and a swivel on the 10mm.
Going from above I have used a 1/4 ratchet and a 10mm angled box wrench.
Here's a tip, put a little gasket seal in the 10mm socket to hold your nut on when you are putting it back. This will keep you from pulling your hair out over a dropped nut. The gasket seal comes right off the tool with a pick.

HMM 3 broken cross-overs... I think you should check your motor mounts while you are down there... =)

X

Remove the pre cat and put in a downpipe at the same time. No reason to keep the pre cat.

Downpipes are wonderful things. Remember the precat was an afterthough added to the FD to legalize it for us emissions testing.

Does anyone know what the horsepower or temerature penalty is for the pre-cat?

You will need to remove the rear turbo's intake pipe. The hard pipe that the rubber pipe attaches to that is connected to one of the air filters. There are two screws and can be recahed from underneath. Aferwards, insert the y-pipe (put a lil oil on the o-ring), then put back the rear intake tube, then you can mount the crossover air pipe. You should have also remove the air pump prior to all this. Make sure all the nuts are tighted or you will blow the metal gaskets. You do not need to remove the pre-cat.

A downpipe usually frees up 10-15 rwhp by itself and will do more in conjunction with other mods. It also reduces the underhood temps by quite a bit.

Well... its done and it was not as bad as I thought it was going to be. I had to remove the pan that covers the transmission to get a decent angle on those @#$%&*! nuts. And I had to remove the air pump to get the old Y-pipe out.

Can't say it added any power but at least I won't be breaking any more cross over pipes.