A while back, a guy shipped me an intake manifold for a cheby 292 that he was having trouble getting boost-tight; it's a DIY aluminum intake. Along with the intake, he sent the TBI's for it that were off of a Honda 1000 RR, IIRC. The intake is set up for two pair of ITB's and boost was in its future. AFAIU, he was going to use Megasquirt and two-stage fuel injection. On the 1000 RR, there is one set of injectors in the airbox that spray on the airhorn and another set in the ITB itself. His intention was to use this two-stage injection system to curb the charge robbing of the Cheby head by using the airbox injectors during primary use and let the secondary injectors in the ITBs kick in at high boost/HP levels.
I'm with Thad though, I think 6 ITB's would be far easier to tune without leaning out a cylinder or two with a home-brew manifold.