Ok finally got around to ripping out the blackbox so i thought i would post up what i did. The main problem is there are no available bolt on filters that I could find on the market for the solex's. So the choice was buy new carbs around $1000-1500 depending on the choice of carbs and thats if you fit it yourself add a couple of hundred to that if you get your mechanic to do the job. The solex's are a damn good carb if they are maintained and i have not long had them cleaned up, so really I just couldnt justify the expense for the minimal extra power gained by replacing them over getting them to breathe better, so what next. There are a number of options for replacing the blackbox and keeping the standard solex carbs, from adapter piping and fitting pancake filters (like the webers) or unisocks or foam beehive filters, or a set up like Tom's (ttmck) that run a pipe between the two carbs with a central filter. In the end I decided to go with seperate pod filters and my own custom design for the fittings, honestly I had no idea what i was doing so really anybody can do this. So to start I opened the manual sat at the back of the van and tried to work out what was what, this was harder than I thought as none of the pics in the manual really looked like what was fitted to the van and with the black box in there most of it was hidden, i knew from a previous breakdown that the hose connected to the right side of the original intake caused the car to run like crap when it came off so assumed i would need to reconnect that, and the other fitting that connected to the same point seemed to run back to the intake, this I identified as the thermostatic vacuum. (see pic) this I concluded i wouldnt need. The only other fitting that connected to the box came off the top of the left carb, and according to the manual seemed to be part of the central idling setup, the only thing I could see was that to tune the carbs it said must remain connected, again i thought thats gotta stay, so that was the start of the plumbing design, two pipes had to stay.