Hey guys i'm new to the site. I wanted to get right into the topic of mods rather than posting in the intro section. I have a 99 black Z28 A4 stock. What i'm wanting to start with is intake, exhaust, headers, gears, LS6 intake, and stall.
I was interested in SLP LM, but have seen several posts saying that it sounds horrible once you add headers. I'm curious which gear ratio would be best as far as retaining the car's fuel economy numbers as well. I have 3.23's stock. If SLP is a bad choice, then I think that i'll definitely go magnaflow.
If a stall means torque converter, which one is the best choice for power gains?
Can't wait to hear from everyone, thanks.

 

As far as your stall (yes torque converter) goes, even for a stock internal engine is recommend around a 3,600-4,000 stall...if you plan on dropping in a decient size cam down the road is lean more towards the 4,000.

Definitely get a tranny cooler if your planning on going with a stall...you can pick one up for about $50-$60 at the local parts store in the RV/ towing section.

I've heard lots of people say the SLP has a lot of Faso at cursing speeds once you add headers...some like it, some hate it lol...but I haven't heard anything bad about the Magnaflow.

You might want to wait on gears till you do decide to cam your car, if not a set of 3.73s would work nice...you also want to look at frame connectors and lower control ARM relocation brackets

 

Magniflow is great. I have one with a cutout welded in. For me I like loud exuast. I couldn't have magniflow without the cutout, it would be to quite. Its great though don't get me wrong. Very comfortable to drive on trips with the cutout closed. As far as stall its one of the best mods for an A4 car. There is some great sponsors on here, just call them and they will help you out.

 

For an auto car the stall upgrade is one of the better mods and as mentioned before get a tranny cooler for sure.

 

If I were you I would figure out a goal for the car first. Figure out if you are keeping it Naturally Aspirated or Forced Induction or maybe some super juice. How wild do you think you will take it.

This is what I would do based on your list from above in order.
1. Aftermarket lid - inexpensive and gets more in air in.
2. Torque Converter - 3200 to 4400 stall (depends on your goals)
3. Headers & Y-pipe - Long Tubes (research on which would fit your needs best)
4. Cutout
5. Catback - go to LS1sounds.com or Youtube and pick your harmony.

This is just my opinion.