Really hard to pick just one:
1. JB4 G5 (with a little E85 in the tank) for the go-fast
2. Dinan FFE for the sound
3. CSL deck lid for looks
but I guess I would actually put them in that order...
..JB4 G5 ISO | Helix FMIC | CP-e Chargepipe | Synapse BOV | VRSF Catless DP's | Dinan FFE | Alpina B3 TCU Flash..