HiRCflyer...A G38 mag coil will replace the points and coil, will work great but weighs the same..$20 plus shipping if you want one...I think C&H has the conversion covered, check their website...

The metal velocity stack is a new thing, maybe they haven't run into the problem yet...
We tried forcing air into the carb on a GT74 many times on a Kelly formula One giant scale race plane a few years ago...It needed to be so rich to take off that it was more trouble than it was worth, and never did run quite right...
The Herbrandson twin drone engines I use on the Unlimited racers was originally a pusher, with the carb intakes facing forward right in the airstream...There was a smalll brass tube in the carb venturi that went into the carb cover that was otherwise sealed..The diaphragm had the same air over it as coming into it..Worked well, but probably no performance increase..
I remember Klaus at the races with his audio tach in his ear, check rpm on the Aerrow 200 twins...I borrowed it for a while but sent it back when we got onboard data loggers, way more reliable and also check cylinder or exhaust temp and air speed.....We've come a long ways