This page will be improved in a while. But until then, I’m now running a Weber 30 DGS carb on my 850, instead of the original DIC. It gives improved throttle response, and the top-end seems to have opened up a bit.
The disadvantage is that no one seems to make an air filter for this carb. But, you can take the old top off of the DIC and replace the DGS’s with that.
One thing I had to do on mine was file down a section of the riser to allow the throttle linkage to swing through its full arc. This is easy to do, but I felt bad about ruining an original part of the car.
I’m sure others sell it, but I got mine from the excellent Vick Autosports, outside of Fort Worth, TX.