I want to compile a list of all bolt ons possible for both M6 and A4s.
It's late and I'm only contributing two:

Headers
ASP crank pulley

Keep it going - EVERYTHING!
Nick

 

intake(lid, k&n, granatelli maf, pace85mm, slp 85mm, bellows coupler, fernco, ported tb, fast toys ram air)

exhaust(headers, modified y-pipe, true duals with x-pipe, cat-back)

m6(shifter, gears, cags, driveshaft, 12 bolt or 9 inch)

a4(torque converter, shift kit, gears, driveshaft, 12 bolt or 9 inch)

suspension(k members, torque arm, lower control arms, subframe connectors, relocation brackets, lowering springs, panhard bar, strut tower brace, upgraded sway bars)

plug wires and drag tires...

 

Here is a list of the parts I have purchased, I think I have almost every performance bolt on for my car besides NOS etc. I've also listed the price below as well.

ENGINE:
Thunder Racing Custom Grind 224/224 - 111 lsa CAM $429.99
SLP CNC Ported/Polished Heads $1,900.00
SLP 1.25" Chrome Silicon Valve Springs $-
SLP Titanium Spring Retainers $-
NGK TR6 Spark Plugs $25.00
Taylor Spiro Pro 8mm Plug Wires $30.00
Royal Purple 5w30 Synthetic Racing Oil $35.00
Metco Beather Cap $40.00
160 Degree Thermostat Part# 1014 $49.99

TRANSMISSION / DRIVETRAIN:
Pro 5.0 "Power Tower" shifter w/ short stick $159.00
Moser 12 Bolt Rear w/ 4.30 Gears $2,300.00
33 Spline Axles $-
Eaton Posi $-
1350 Yoke $-
T/A Performance Girdle $-
Royal Purple 75w90 Gear Oil $10.00

EXHAUST:
SLP Long Tube Headers $949.00
SLP LoudMouth Cat Back Exhaust w/ Dual/Dual Chrome tips $349.95
Off-Road Racing Pipes $20.00
O2 Simms $90.00

INDUCTION:
SLP Cold Air Induction $129.99
Holley Powershot Filter $45.00
SLP Air Box $99.95
SLP 85mm MAF $159.99
MAF Translator $150.00
Thunder Racing Ported Throttle Body $150.00
Baker Hose $49.00

SUSPENSION:
SLP Strut Tower Brace $99.95
LG Motorsports Heavy Duty Torque Arm $495.00
Energy Suspension Transmission Mount $30.00
BMR Boxed Sub Frame Connectors $159.95
LakeWood Drive Shaft Safety Loop $49.99

APPEARANCE / MISC:
Custom Painted "Roof Band" 71-U Sunset Orange Metallic $120.00
Convoluted Tubed Engine Bay (blue) $35.00
Hood Badges - chrome SLP logo $-
G2 Chrome World Challenge Wheels $2,000.00
Nitto 555R Extreme Drag Radials 275/40-17 $300.00
AutoMeter 3-3/4" Tach with shift light $79.00
Escort Solo Cordless Radar/Laser detector $180.00
SLP Line Lock Kit $139.00

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by FEAR THE LS1:
<strong>...I think I have almost every performance bolt on for my car besides NOS etc.

ENGINE:
Thunder Racing Custom Grind 224/224 - 111 lsa CAM $429.99
SLP CNC Ported/Polished Heads $1,900.00
SLP 1.25" Chrome Silicon Valve Springs $-
SLP Titanium Spring Retainers $-
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">All of those mods are considered Internal engine mods... (ie not "bolt-on's")

Here's the "Bolt-On" Stock Internal (SI) mods I have done to my car:

Whisper Carbon Fibre Lid
Whisper Ported MAF Ends
Whisper Ram-Air
Whisper 1" 7/8 Headers & OR Y-pipe
Whisper Cat-Back
Cut-out
K&N Filter
ASP Pulley
BMR Throttle Body coolant by-pass (!TB)
160° Power Stat
Ported Throttle Body
NGK TR55 Spark Plugs
Timing Tricker (!TT)
Ed Wright Tuning
SLP Fan Control Switch
B&M Super Trans Cooler, 24,000gvw
Pro Yank 4l60e Tranny
'98 Flexplate
Yank Thruster Pro 4200, Torque Converter
Energy Suspension Poly Torque Arm Mount
Energy Suspension Poly Trans Mount
BMR Lower Control Arms & Panhard
Strange 12 bolt w/3.73's
15" Welds, ET Streets and Skinnies (Strip)
AFS ZR1's 17x9.5 & 17x11 w/Nitto Extremes & 315 Drag Radials (Street)
Kenny Brown Double Diamond sub frame connectors
GM WS6 Hood and lower airbox

I now have 26x9 Hoosier slicks, also have a Carbon Fiber Driveshaft and tublar K member waiting to be installed. Shooting for some Bolt-on 11.5's in a few months <img border="0" alt="[devil]" title="" src="graemlins/gr_devil.gif" />

 

I was gonna say...anything "external" is a bolt on.
Nick