06' would have a charcoal canister.
Common mods would be to change the exhaust. I believe your bike came with a catalytic converter as well. That could be swapped out for different headers.
You could remove the blinkers.
Many folks with early Monsters would remove the rear fender, guard, then cut the rear loop off the frame. They make plastic plugs and aluminum plugs to fill the void in the tubing. Ducati Monster Tail Chop . Com offers easy plate and brake light relocator kits.
Rear passenger pegs.
Front sprocket cover.
Of course it's all dependent upon where you live, your local laws, codes and ordinances, as well as what you plan to do with the bike as far as riding it.
09 Aprilia RS125 plated< NEW info> Now a 144 and back on the road!
06 Paul Smart Sport Classic NFS ever.
08 S4RS Tricolore #081 NFS ever.
The pink Monster has moved away.
97 900SS CR
72 Norton Commando 750
03 KX60 with S4R rear shock,Honda CB350F, Hodaka Ace90, 3x Yam-YGS1, Yam-CS3 200, Vespa small frame, Gilera 106, Puch Sabre, Puch 50 Boy Racer, Benelli 250, Benelli 360, Honda CB350T, and many more.