ducatipaso.org

Not an upgrade, an alternative.
No increased performance.
The diaphragm on vacuum pumps do fail sometimes so less reliable IMHO.

there are a few advantages. Sure a vacuum pump can fail. Same as an electric fuel pump. I've heard more about the latter being defect than the first. However, other than for the electric pump you can get spare parts for the vacuum one. Mikunis sells the membrane.
Of course adding a fuel pressure regulator will do the same as switching pumps but to me adding another piece instead of just using a pump with the proper fuel pressure makes no sense. Also with the underpressure pump there's one item less putting stress on the weak electrical system.

I guess its an upgrade in the sense that its newer and doesnt reqire a reg or a return line . One of the theories about the poor carburetion was that the electric pump puts out to much pressure , whick it does but it was rumoured to cause over filling the float chamber . Some peeps fitted a decent regulator , some fiddled with the flow rate of the return line as a means of adjusting seen fuel pressure at the carb . The vacuum pump is not capable of enough pressure to require either a reg or a return line ,it does however provide ample flow to power the motor. If your Paso in running well ( tiz a very rare bird if it is ) I doubt youd see a difference , but its not hard or expensive and is a worthy mod .

I placed a fuel pressure regulator after the fuel pump and found the changes in air temperature affected power output the greatest. Colder weather meant higher air density & oxygen, so on that day I would increase fuel pressure to the Webber. Just running it with a simple return line to the tank made the engine run mostly awful.