I thought I would start this up as I progress towards making one of these carburettors work. The Bouncy Bus has a 1600TP engine. It had a worn out 34PICT-3 carburettor fed from an oil bath air cleaner. The exhaust fed into a 4:1 header and an EMPI dual quiet pack exhaust chosen by the previous owner. One thing that became clear was that this combination was not working well. Rather than buying a clone 34PICT3, I bought the DFAV kit from VW Heritage. On the box there is a sticker saying "call this number to find out about correct jetting for your engine" . I did and they told helpfully told me to go and find a rolling road as they are hard to set up. Instead of doing that I decided to go for a home brew approach, and do some research. But first I slapped the carburettor on and went on a 1000 mile trip. And it turned in about 20MPG and cruised at 67MPH. It idled badly and left black marks all over the rear bumper. I had fitted the pretty chrome filter on the top and left the oil bath behind. The exhaust header and tailpipe were replaced just before the trip because I blew up the rusty exhaust with a backfire. Research 1: You need a lot of heat to vapourise petrol in this carburettor setup. Heat comes up to the base of the EMPI brand carburettor support riser, from the exhaust through a pipe connected across the outlets of cylinder 2 and 4. Not perfect, it should go from 2 or 4 , up to the carburettor base and then back down to the tail pipe to keep hot gas flow through the inlet manifold. (reference aircooled.net) As it was, there was an increase in top speed and a lot of lurching and cold running splutter and kangarooing. On the Autobahn no problem. Increasing preheat : I decided to reinstate the oil bath air cleaner as I had one. It originally provided a thermostatically controlled source of warm air from the cylinder head, as required to help the carburettor. But I needed an air box to adapt the output of the oil bath air cleaner to the large carburettor top panel. So first I made a prototype out of pvc pipe and tumble drier vent pipe held together with polyurethane glue. This improved the running and reduced the lurching. Next I made one out of aluminum sheet pop riveted together and sealed with fibreglass car body filler then painted. This bolts onto the top of the carburettor leaving just enough clearance to lift the carburettor with air box attached over the studs in the inlet manifold. Alternatively I have seen air boxes for this carburettor for $149 on ebay which allow you to connect an air hose. End result is the carburettor and the inlet manifold do not feel cold to the touch any more when the engine is running. I noticed that once the vacuum hoses were all connected up, the engine seemed to run at higher max RPM if it sucked hot air from below through a 50mm hose rather than through the rather tiny nozzle on the air cleaner. So taking notice of the fixing spring for the actuator on the bottom. I cut 20 mm off the air cleaner inlet nozzle making the hole bigger looking more like the size of the hole on the later plastic air filter boxes. Then I bought a few jets off Eurocarb - changing the out of the box jetting which is pretty poor and where I couldnt set the idle mixture at all. I first changed jetting to Primary Idle 50, Primary Main 135 and Secondary Idle 60 and Secondary Main 140. Still smoky and low economy but the lurch when you put your foot down started to reduce. Then I finally got round to fitting the PLX devices Inc. air fuel ratio meter. This uses a wideband lambda sensor in the exhaust to gather information about the fuel/air ratio assuming that the engine is working reasonably properly. This cost $200 via ebay. Which by the time tax and duty was paid was about £200. Thats the complete kit including dashboard display, engine bay computer box, and lambda sensor. In order to fit this I bought a welder and learnt to weld well enough to get a big lump of metal welded to thin pipe. I had to extend the cables from the computer in the engine bay to reach to the dashboard. I decided to use 4 core screened audio cable as this was lying around and there are 4 wires and an earth going from engine bay to dashboard. From reading around , I discovered that there is a target Air Fuel Ratio of 14.7 used for best emissions in mass-produced vehicles but this corresponds to maximum exhaust gas temperature, not peak power or efficiency. And the VW engines like to run a bit richer because of their design. But when they are not working hard, then running leaner can be more efficient. And on my first drives with the AFR meter, it showed how bad things were. While warming up the engine ran richer than 10:1 and it spat soot and water. Warmed up it was not much better: driving up a slight hill it worked around 11:1 and on the motorway it might flicker to 13:1. Only time you could get it to run lean was stamping on the accelerator, which corresponded to a lurch. Now changed jetting to Primary Idle 45, Primary Main 125 and Secondary Idle 60 , Secondary Main 150. This is similar to some recommendations on aircooled. net. While cruising, the AFR sits around 14-16:1 unless wide open throttle where it drops to 12:1. I am not finished here but already I can state : The engine runs smoother, accelleration is not all confined to a burst around low throttle. Surging and lurching has mostly gone despite the AFR still becoming quite high when acellerating. The engine runs quieter and cooler now , about 10 degrees C as far as I can tell.