I have a modified 400E with the 2.82 --with a chip -with performace exhaust-
Stats --0-60 in 6.2 seconds --1/4 mile best was 14.9 with bad plugs -wires -caps and rotors-- After I replaced them I would guess it was good for a 14.7 or so . Only way to get faster is to toss out more things not needed -I have an aluminum race seat and I have removed the rear seat as well .
The only other modification that I know of besides spending 5k on the engine is to just spend $2000 for a nitros oxide system then you will be in the 5 's to 60 and 13.5 s in the 1/4 mile . As far as costs go just see the picture I have attached. If you can do the work yourself this is a lot of bang for the buck .
I had this car on here a while ago for sale for only $3800 or so and no one was interested and that was with all the modifications!

http://userpages.itis.com/eurocars/FM400.JPG