jmofield

The car 1998 formula a4 with 3:73's and lm1 catback. Just traded an rc car or unknown brand of stainless long tubes race style off a 99 t/a. What all Will I need to make these work? Do you need two 0'2 extension's or one? What cheap y-pipe work's with lm1 catback?

conan

iTrader: (5)

You'll need O2 extions, new GM exhaust manifold gaskets. Replace your spark plugs and wires if there old. Also you'll need to block off the egr hole in the intake manifold.

Longshot LCMS

iTrader: (1)

You don't need O2 Extensions. Switch your upstream and downstream O2 sensor pins in the PCM.

jmofield

will regular gm manifold gasket's work?

conan

iTrader: (5)

Yes, they are a MLS gasket, don't use paper gaskets. Also you're going to need a new Y pipe as well check out texas speeds ORY.

conor.davis

iTrader: (20)

Before you get a Y pipe you need to know which headers you have unless you don't mind modifying the Y.
All Y pipes are not all the same, just as all header collectors are not angled the same once installed.
Look into replacing motor mounts also.

Gordo78

iTrader: (3)

Yes i would in this case. A plug and play extension would be a lot easier for 90 percent of people. You'll need a pair, one for each side O2. BUT OP you could do what he said if you feel like playing with wires.

As stated figure out what brand they are before you get a Y or you could have a good exhaust shop fab you one up with a flowmaster merge. Poly motor mounts are a good idea too, you will probably have a banging Y if you don't... I sure did.

Longshot LCMS

iTrader: (1)

It's really not as much of a pain in the *** as it sounds. Find a print out of which wire does which in the ecu and swap the pins. Takes 5 minutes, requires no cutting.