I have a Hybrid 1406 on my R2 Avanti. I took JP's idea of the AFB top on the Edelbrock bottom and did a couple of mods that have made the car perform better. One change that would only be necessary with the AFB top installed is the use of the original AFB primary and secondary venturi clusters. The primary clusters of the Edelbrock have shorter vent tubes and rather than being separated from the air stream though the throats they would be exposed to it. I found that once I went to the AFB clusters throttle response and FUEL MILEAGE greatly improved. The secondaries had a slightly different configuration so I changed them also but it may not be critical, the primary change is. Before the change the car needed a larger jet to perform properly. The second change is subtle and easy but helped eliminate a big drop in power at high RPM's. The secondary air flap on the Edelbrock doesn't lay flat like the AFB's. In a naturally aspirated sitiuation this positioning probably helps it open a little quicker. I think in a blow through situation it's angle allows it to be pushed shut or flutter at high RPM and full boost. A little grinding on the counterweight allows the flap to lay flat like the original R2 AFB.          The third mod is to make a hard connection on the secondary linkage. Both the AFB and the Edelbrock can benefit from this mod. The secondary plates are not directly connected to the primary. There is a fairly heavy spring that opens the secondaries once the tension from the primary linkage is released and the choke is fully open. If your choke isn't opened all the way the secondary plates on the AFB and the E Carb wont open but the pedal will still go to the floor. I may not be explaining it well but the bottom line is that full boost can overpower the spring pressure and keep the secondaries closed. I tack welded the linkage together although there may be other ways. I noticed an instantaneous change in full throttle performance after I did this. I've spent LOTS of hours making the Hybrid carb work. The Avanti has run a best of 15.097 and gets 22 MPG on the highway with the 3.73's and the 700R4. It doesn't leak ( anymore than the original AFB did, mild seapage after lots of hard driving ), idles smoothly in the hottest weather and responds as crisply as any carbureted car possibly can. My next mod is not to the carb itself but to use an "O" ring for the carb hat rather than a paper gasket to get a better seal and pick up a tiny bit of hood clearance. Tack weld at the screwdriver tip.