I am just trying to make a clear cut thread that can be a sticky and a "Go To" spot some quick modification information/guide. I know we have a lot of this information already buts its quite scattered through out the forums.
For example here is "Audizine's" stages for S4's.
Full write up here:
Rich's Quick Reference Upgrade/Mod Guide for n00bs
Stage 1: Chip.
Generally 320bhp. Used: $200-$500, New or Custom: $600. Easy to find used.
-APR: is the “smoothest” and most “like stock” in its power curve, boosting to 18 or 19psi these days, but older software will be 17-18, tapering off to 15 or 16. Generally claims 320 bhp. You know you have an APR if you can change “programs” by holding in your cruise control button for 5+ seconds while the ignition is on but the car is not running. If your CEL starts blinking after holding it for 5 seconds, you have an APR chip.
-GIACX: is the most aggressive. Boosts to around 19-20psi now, tapering to 16-18 which is really getting out of the efficiency range of the K03 turbos. People do love this chip, though.
-REVO: I don’t know anything about it. It’s probably similar to the APR.
Stage 2: Chip + Catback Exhaust.
Nets you another 7-11 bhp. $500-$1,500 for the catback
-AWE Twin1 or Twin2: The Twin1 is a great , very aggressive sounding exhaust. Around $1,200
-Vibrant: Also pretty aggressive sounding, very good value for the money. Not quite as much flow as the Twin1, but it does sound very good, if not a bit more tame than the Twin1. $500-$650.
-SSAC: Cheap. Sometimes it fits, sometimes it doesn’t. Since they’re so cheap, it usually works out to be cheaper to take it to a shop and have them fix it up to make it fit, but sometimes it will run you extra. Kind of luck of the draw. It’s a copy of the Twin1, but comes as a FULL TURBOBACK with NO cats, so if you need cats you’ll have to buy them from somewhere for extra. These will throw a code without cats, so you’ll need to do some fancy things with your O2 sensors like run spark plug non foulers ($5). If you have a welder and know what you’re doing, this is a no brainer because of how inexpensive it is. People are often selling the DPs or test pipes in the classifieds. $400
-Milltek Super Dual: Much more “refined” sound. Aka a lot less loud. $1,300
-Borla: Also quieter and more refined. $800
Stage 2+: Chip + Catback + DownPipes (aka Chip + Turboback)
Nets another 20-30 bhp and helps turbos spool quicker. $0-$2,000 for the downpipes/turboback. You generally don’t need 3” DPs until you have bigger turbos, but it can’t hurt.
-Piggies: Home-made downpipes using the stock DPs: you take them off, gut the precats out, relocate the front O2 sensors or use spark plug non-foulers on them. They can net you a nice power increase on the stock turbos. You can also buy piggies from VAST for $300 or something like that, or find them used in the classifieds. $0-$300
Link to making piggies:
DIY: B5 S4 - Removing DP's to make Piggies (For 6spd)
-Other DPs: Tons of places make DPs. I don’t know many off the bat, but I think they’re generally all fairly similar. R.A.I, 034, and many others make some damn nice ones. Most 3” DP sets cost around $1,000-$1,500.
Stage 3-: New Turbos without fueling/proper intercoolers. 300awhp-350awhp $2,000-$4,000
Stage 3, 3+, 3+++++: New Turbos with proper fueling, tuning, ICs, etc. 375awhp-"smoking 996TTs" $3,000-$$HOLY F$@K
-K04s: 375awhp-430awhp. Some make more some make less. $3,000-$7,000 +
-RS6s/Tial 605s/GT2554s: 430-500+. They can get you 450 without much trouble on a stock block, and can get to 500whp or over with decent tuning/race fuel/meth. Anything at/near 500awhp you'll want to do rods on the engine which can be done cheaply, but can also end up costing $5,000+ when you decide to replace other things "while you're in there" when all is said and done. $5,000-$12,000
-Big Garrett Turbo (GT)/Tial 770/Single Turbo: 500-???whp This is kind of limitless, because everything starts to get all custom in this range. With some GT kits you can get away with just rods, that’s the 500-600awhp range. After that, you better have a damn good tuner, or it’s time to build the whole engine. The engine should probably be fully built. Many do 2.8 heads, and most upgrade the valvetrain to rev higher and enjoy the powerband. This thread doesn’t need to get into big GT kits. $8,000-“the family farm.”
End Stages.
