Plug Fouling with TPIS Mini-ram

I have a ZZ383 GM crate engine with a TPIS mini-ram fuel injection system, with 30lb injectors. The engine management system is speed density. I have been having a problem with cylinders 7 & 8 fouling out the spark plugs. All other cylinders are burning clean. In addition my block learn # was 108, which indicates rich conditions accross the board. When this motor was set up initially, the minimum air adjustment was at base minimum with the throttle blades completely closed, thus allowing the IAC to control most of the air at idle. Assuming the possibility that adequate air may not be reaching the rear cylinders at idle, I have adjusted the minimum air so that the throttle blades are much more open and also reset the TPS to read idle conditions, in an attempt to allow for the availability of more air. I have also reduced my fuel pressure in small increments from 45psi to now at 41psi. As a result my block learn numbers have increased to 118-120 at idle and 120-130 during normal driving. I have not driven enough miles yet to determine if the plug fouling issue is improved. Does anybody have any thoughts or suggestions on this ? Am I headed in the right direction ?

IMO the mixture must be extremely rich to foul a modern ignition system.
Are you sure it's fuel that's fouling them? Is it possible they are becoming oil fouled from stuck rings etc?
I might suggest before going further, try 2 new plugs and plug wires in the offending cylinders just to eliminate the possibility of an ignition problem due to defective or damaged parts.

Thanks Magic. All the parts associated with this engine are new. The wires are 8.5mm MSD super conductor. It is possible two of the new wires could be bad and I will swap them out as you suggest. I don't think its a ring or valve problem as I have done compression and vacuum testing. I have found some information this morning on the net from individuals having the same problems with the TPIS mini-ram. They are assuming as I am that its an air distribution problem due to the design. If that is true, I don't mind compromising by having to replace those plugs more often. What I am hoping, is that if I can get my block learn to a better number then the motor will be more efficient and as a result the spark plugs on the affected cylinders will last a little longer. Over all the car runs very strong.