Mickeyrx70

Without question it's the double din radio bezel and Kenwood DNX 891HD head unit with Garmin navigation, backup camera and blue tooth from Doubledmods. The Kenwood literally transformed my listening experience from so-so to WOW using the same speakers.

skydiven4fun

Supercharger without hesitation, new head unit I installed is not too far behind, but nothing compares to a blower coming online at full tilt it's just too much fun

bjones7131

C6 Z06 wheels and new Hankook tires

sfc rick

Can't even say which ONE is....just too many to choose from.

OK.....red stripe.

v98roadie

Hands down, 3.73 gears in my 02 A4 followed by Corsa Sport SO FAR. The car sounds and performs like a Vette! I have a lot more tinkering to do, I haven't even started on the interior.

Chicago1

blower

Toque

Its hard to say. I like all my mods.

But if I had to choose it would be these upgrades

Heads/cam/header/intake upgrade (471rwhp/441rwtq)
CCW SP500's
LG GT2 coil overs
Corbeau Seats
Morimito Bi-Xenon HID projector lights
LED interior upgrade.

Toque

DDaaryl

Mine is an aftermarket cover I got at K-Mart for $22. Otherwise my vert is unmolested to retain better value and reliability

Evilash

Tough choice.
The ls2 drive train for the power to keep up with new stuff to keep my interest in driving it?
The Radio Flyer Light Cannons so I can drive it at night?
Or the Featherlight coil overs so it isn't crushing my spinal fusion so I can drive it at all?

Fast one

My A4 no pushbutton shifter with led indicator ****.
In Reverse.

In fourth gear

J-N-M

My favorite mod would be swapping the A4 out for the M6. Better gas mileage and 100 times more fun to drive in my opinion. And by doing it at home I learned a ton about my car.

jd_black_00

I don't regret any of mine... Full carbon fiber targa top might be the most original mod I've done...

Laser Guided

Forgestar f14s in toyo r888 tires
For the aesthetics of the wheels, being able to clear big brakes, and the massive performance increase from the tires

zdeckich

My favorite mod by far is cam and full exhaust.

zdeckich

My F14's are probably my 2nd favorite mod. Love the wheels.

Wicked Weasel

Ls7....

7LitreC5

Wet sump LS7.

Chad Dallas

Esky cam??? Im looking into getting a cam for my c5 all ive done to it is billy boat exhaust and bbk intake but do not know wether it will require getting different heads and to which cam to get should i just call a jegs or summit tech support for these questions or maybe u guys can help???

'Shifter

I've yet to do any "speed" mods, but I'll say the C6z brake conversion would be my favorite so far.

DrRaySomeDay

It was a 150 shot for a while, but the A&A supercharger is always on and changes the whole experience of the car.