ADAM,
The easiest way to improve acceleration in your car is to remove the entire interior and install a 4.11 gear in the rear!!
Just kidding but the truth as these cars are hard to improve on. Some real suggestions:
1. NOS kit, best bang for the buck, but doesn't last too long.
2. Supercharger or turbo kit, now hard to find as these cars are aged past the marketing limits. If found, $5k-$12k!
3. Reworked transmission valve body for first gear launch...cost $450-1200.
4. Put in a later 3.2 drivetrain.
5. Trade up for a 400E or 500E and have fun!!

Good luck,
Tobias MB
300SE, 300CE, 190/5.0