Since you have the turbo timer installed already they may use that as a reason to void your warranty? Someone else may chime in with a better answer. I might wait a while myself before any major mods.

That's actually a good idea to tell them. I bet most of the Saab mechanics have not worked too much on these cars to notice what it is.  Hmm, I do like the boost gauge function...

Per the law in order to not honor your warranty (lets not even get into "voiding" it) they have to prove that the modification caused the failure.  If you have an upgraded turbo I wouldn't count on them covering internal engine damage, but they can't say that your seat broke because you put a boost controller or something.

In reality many dealers are uninformed as to the law or sometimes will lie becuase paying for service work out of pocket is way more profitable for the dealer than warranty work.