If you change the gearing, you will need a programmer, and there are not that many choices, tunercat would be the only way I would go. Also with the tuner cat you can do the basic stuff, like change the tire size, make your fans turn on sooner, etc etc besides messing with your fuel curve, etc etc.
Second, in a4 going to 3.42 will only gain you a few 10ths, if that, in the quarter. Not as much as you think, and will cost you only a few mpg's. A properly running a4 gets 16 city 25 hwy, (maybe a little more hwy). with the new gears, figure 15 and 23.
If you liked the Nitto 555's, then go with them, I prefer the BF Goodrich KWDS a/s since I am in Chicago and drive my car in winter, otherwise, drag radials or just normal KDWS summer tires.
your going for a 13.5, stock rear end stiffing panhard, sway, all that will be fine, look at BMR, UMI that are from jegs or summit if you want to upgrade, complete kits are right around 1000, and not worth it for a 13 second car. My advice would be front strut bar and frame connectors first, then worry about replacing the stock components in the rear.
Have you given braking any thought? Good rotors and pads go a long way.
Headers, not to many avail, pacesetter longtubes with the y connector seem popular, but they are not "great" headers, but do work and seem to last somewhat a reasonable time. Keep the air pump if you have it. You will need o2 sensor extentions and it will take a little bit longer to "light off" your cat but not enough to trip the computer.
torque converter, hmmmm, have to ask someone else. You can get a better time with the right one, but then daily drive it, not to sure which one would be best.
Good luck
Second, in a4 going to 3.42 will only gain you a few 10ths, if that, in the quarter. Not as much as you think, and will cost you only a few mpg's. A properly running a4 gets 16 city 25 hwy, (maybe a little more hwy). with the new gears, figure 15 and 23.
If you liked the Nitto 555's, then go with them, I prefer the BF Goodrich KWDS a/s since I am in Chicago and drive my car in winter, otherwise, drag radials or just normal KDWS summer tires.
your going for a 13.5, stock rear end stiffing panhard, sway, all that will be fine, look at BMR, UMI that are from jegs or summit if you want to upgrade, complete kits are right around 1000, and not worth it for a 13 second car. My advice would be front strut bar and frame connectors first, then worry about replacing the stock components in the rear.
Have you given braking any thought? Good rotors and pads go a long way.
Headers, not to many avail, pacesetter longtubes with the y connector seem popular, but they are not "great" headers, but do work and seem to last somewhat a reasonable time. Keep the air pump if you have it. You will need o2 sensor extentions and it will take a little bit longer to "light off" your cat but not enough to trip the computer.
torque converter, hmmmm, have to ask someone else. You can get a better time with the right one, but then daily drive it, not to sure which one would be best.
Good luck