No chip is specifically available for the 400E that I know of; the ones available for the 500E run $600 and provide (if lucky) 10 HP -- most of us who have them have certified with dyno results that they are of dubious value.

RennTECH makes an increased-volume air intake box that will probably also work with the 400E. It costs $1,000 and again is supposedly worth 10 HP -- again dubious. You're paying a lot of money for that 10 HP.

Intake solutions such as K&N filters don't provide any measurable gain, and allow through increased amounts of particuate matter. Again, several hundred dollars for no/negligable gain.

On the 500E, there are only two real ways to get significant HP. The first way is to install nitrous oxide. That's worth 100 HP, but you will pay nearly $3,000 for the Bergwerks.com kit + accessories that you need, and then at least another $1,000-1,500 for installation unless you want to do it yourself.

The second way to get significant HP on a 500E is to punch it out to 6.0L by either boring, stroking, or a combination of both. These solutions would run you $10-15,000 at a minimum, for obvious reasons.

All other solutions are piddly and not worth the money. Options available for hoppign up a 400E are even more limited.

Cheers,
Gerry