Andy, regarding the throttle return, just check wether it is a carb issue or cable issue. With both cables removed from the carb rack, actuate on the rack to see if the spring is doing it's job and the carb linkage works smoothly, lifting the carbs needle etc. Then, with the cables still removed, pull from both of them alternatively to see if you can "remotely" turn the throttle grip, and see if there is some friction. It should be smooth as silk. If it's not, you can check a) the bolt below the throttle that adjust the throttle friction -sometimes used to keep the throttle on while warming up the engine-, then the cable lube, and lastly, remove the switch housing to check that the throttle tube is free inside and the cable routing is good too.
Regarding the engine-to-carb rubbers, are they are harder than the airbox-to-carb, that's where the big problem lies. As you know, all of them are at an angle because the distance between intakes in the engine is bigger than the distance between individual carbs. For that reason, there is only one position in wich you can have the four of them aligned. Turn any of them and, because of the angle, the rubber mouth will either move up or down, therefore ruining the alignment. The easiest way for me was to untighten the engine clamps, so I can check for the alignment first -just place the rack in front of the rubbers to visually check alignment and separation-, and once it was spot on, slide the carbs all the way in and tighten the eight clamps.
Raul
