I should probably read through this thread in its entirety once again but I think I'm having more of a cold start issue with the new pump/sender unit. I know my entire cold start system is working 100% and I do have Dave McKeen's RPM relay which primes the fuel system for one second just before startup. I usually don't have a hot start problem that I've realized.

There are times where I'll start my car and it fires up just fine when it's cold. Other times, it takes about 3-4 cranks at about 5 seconds each. It acts exactly like a fuel problem...kind of like when you go to start the car up right after putting the intake manifold back on. It's a bit hard to start, finally catches, sputters a bit for around 5 seconds, and then all's well. For me, I can only imagine that there are times where the check valve functions correctly and other times where it sticks open. And it makes sense: if the valve sticks open, the entire fuel loop would be open and it would be difficult for even the upgraded RPM relay to prime the system and develop enough fuel pressure at the injectors. Almost like the system would backfeed if the check valve were open, if I'm correctly understanding the system design.

I'm guessing the check valve would solve the problem and it looks like they might've just gotten them back in stock. I just ordered one off the website even though it says they're not in stock. I had called them earlier today and the girl on the phone told me they should be in stock in about a week or so, but then later in the day there was the option to order one on the website. So we'll see!