RE: Welcome to Club SAITO !
Old Bird:
Welcome, sir.
Ernie:
Looking back I see I missed a couple of your questions.
The only ones prone to intake leakage are the mid block engines, the ones with the carb screwed to the back plate and a curved pipe for the intake. The pipe tends to vibrate, causing failure of the o-ring at the cylinder end. The FA-72 seems to be the worst of the lot for doing this. I've found a thin smear of RTV keeps the pipe from vibrating, usually prevents any further problem until the next tear down. Than another smear of RTV...
Saito engines have good fuel draw even without muffler pressure, the pressure just helps and often is not necessary. If you put the tank back on the CG though, a pump is not a bad idea.
I've had mixed results with a straight pipe. Originally I ran a straight pipe on my US 120, but couldn't get a consistent run This was a true straight pipe, with no restrictor at the outlet end. Put a standard exhaust/muffler system on it, no further problem. With a pump it should work fine, the pump will give you the consistent fuel feed. My "New" FA-120 has the restricted straight pipe, I don't anticipate a problem with it.
Bill.