It's got an LT1 engine cast iron block alum with reverse flow cooling and an opti spark up front instead of a dist. It's responds to all the typical mods, heads, cams, headers and of course the odbII is programable. Your rear gears if memory serves me would most likely be 3:23:1 and it should be a posi which is limited slip by the way. There were other gear options and the stick and auto got different gears stock I believe...

 

gears are 3.42's for 6 speeds and 3.23's for autos. Don't wanna break the bank then go with a good intake (slp makes a good one), headers, and a catback. I suggest magnaflow. They have a new one that sounds excellent! Deep, crisp tone and it purrs at idle. If that isn't good enough come back

 

as stated M6 got 3.42s
A4 cars were 2.73 with 3.23 optional, all Z28 should be posi regardless of ratio

for an M6 gears are all important, for an A4 a nice stall (gears if you like)
a CAI kit and headers/cat-back are essential

also I like to remind people to not overlook suspension
SFC's are must mods imho, any V8 4th gen (LT1 or LS1) has enough power to tweak the body

check out camaroz28.com

 

If it's an A4 tranny the gears could either be 2:73's, 3:08's or 3:23's from the factory. If someone has changed gears in an A4 more than likely they are 3:73's. If it's an M6 they are 3:42's from the factory but again if someone has changed gears they are probably 4:10's. Performance again depends on tranny. A4 best bang for the buck would be a stall converter. Go to www.ls1tech.com alot of LT1 info on that site also.