Huh.... Well that doesn't sound like the injection system to me so much anymore....
Let's go back to basics
Is there fuel in the fuel bowl now? (open the drain level to check)
Could the fuel gauge be giving a bad reading? (are you close to empty?)
At 1/4 tank there's an issue with the pick-up in the tank where, because of a crack, it starts sucking air.
How's the IPR look? Connector OK, no bare wires? The tin nut, that holds the coil on, hasn't fallen off?
How's the oil? Not low?
The AE will monitor the ICP pressure and IPR duty cycle (%). What do they look like?
As a test you can even unplug the ICP (not the IPR though) and the computer will set a default value for the IPR to run on (it will set the CEL too of course) but if it didn't do it with the ICP unplugged it's a good indication the ICP is the problem. Another good indication of a failing ICP would be oil seeping through it and into the electrical plug on it (take a look)
The whole "15 times in a mile, then starts right back up" sounds more like fuel delivery to me and I'd be looking at everything related to that too.
Maybe take a look in the filter housing and at the filter (might be a good excuse for a change