I have seen a post where a guy put and eaton m90 supercharger in his DI, and he was pretty happy with the results. I have read some about these engines when buick made them. I think they would have held up then with the way the sleeves were made, but now I think you would have a rolling compression bomb.

 

Wow, thanks for all of the tips.
I have only filled up once, but it was premium Shell. I have about a 1/4 tank left (only have a 3 mile commute) so we will see what the rest of the month holds.
I bought a can of seafoam. Actually, I bought a lot of stuff from them (Deep Creep, silicone spray, the induction cleaner with the special straw...). On my next fill up I am planning on putting Seafoam in the tank. Also going to clean the throttle body and replace the air filter. I need to look in the Rave manual for the fuel filter location on these things. I will check out the plugs/plug cables.
Luckily, the PO had all maintenance done at a Rover dealership, and all of that stuff showed up on the carfax when I bought it.
I am not looking for a hot rod, but I have driven several '04 Disco 2s while looking for this one and I can tell I am running a little sluggish compared to others.
Oh, as to the puffing sound, it seems to be originating near the driver's side firewall, but I can only hear it when I am accelerating. Thanks again guys.

 

You won't be changing the fuel filter, it is built into the pump assembly in the tank. Puffing sound could be an exhaust leak, and if you do the Seafoam induction cleaning you will see where it is leaking (smoke billows out for a few minutes).