what should i do with it? if you take it off, you get an error code on the rev counter, dont you?can you just leave it in the engine bay?

You have a couple of options assuming you are using the bike clocks. Assuming you already have the EXUP valve then simplest answer is just to leave it in the engine bay or under the scuttle. You could also make up an electronic circuit to mimic the EXUP which will cost a few pounds with bits from Maplins

Have a look at Bob C's post in the following.

Linky