B16 runs rich on start-up

My CRX with B16 has developed a problem where it's hard to start. The problem is worse when it's warm. I thought it may be leaking fuel injectors, so I spent $125 and had them cleaned, but this did nothing.
It starts ok when cold, but when warmed up if I shut it off and start it up a few minutes later, it cranks awhile then once it starts, it runs rough (and exhaust smells like unburned gas) then clears out.

What does the purge solenoid do? I do not have one connected. THe motor also has an aftermarket fuel pressure regulator on it.

Any ideas??? Thanks!