1990 NA 300zx Fuel System Gremlins

[KDS_cars]

Its been a while since I have been on here but im stumped once again. I first got my 300zx and found it had a bad injector. no big deal the old styles fail. I got all 6 new style injectors and put them in(stock CC for NA). I kept the old fuel rail using some little adapter cups that let you put the new styles in the old rail. It ran great for a while then once again, misfire. found out it was cylinder one and tore the top of the motor down again. I pinched an injector o-ring causing fuel to rush into the cylinder just as if the injector was stuck. Replaced all the o-rings with new ones from concept Z corectly this time. used petroleum jelly and twisted them in till they set. At this point I was still worried so I put light pressure to the rail with air to check for leaks. none. Put it all back together and drove it for the second half of the summer. I parked it over winter having no issues at that point. started right up recently once the snow and salt got washed away. drove it for over an hour and with to much trust took it to far. Parked it at a restaurant. Once I got out it took longer than usual to start. cranking over maybe 10 seconds or so.(it did not hydro lock) drove it out the lot, misfire. Tried to limp it home and less than a mile after leaving it lost 1/4 tank of gas. parked out side an auto zone to find the gas was fleeing out only the left side exhaust. I'm not sure where to start. I'll pull apart the motor and test all I can. ohm injectors, pull plugs and run it prior to find out which cylinder misfires. Any ideas what it could be?
I have so far replaced:
Injectors: old to new style
Injector o rings: from concept Z
Fuel pressure dampener and regulator: damper failed letting fuel suck into the plenum.

All that has not been changed is the rail itself but I pressure checked it with air prior and found it fine. bad o-rings again? failed fuel rail or faulty injector? I have also checked all the coil packs when i changed the o-rings and found them fine.
i'm going to look into it but I wanted to know if anyone else has had so many issues with injectors or may have any ideas of things i'm overlooking? Any help is welcome.

Also I found no external leaks after this. Nothing above the motor, around injectors or around fuel lines. it also droped more cylinders as i drove which makes me question o-rings / injector as that shouldn't take out other cylinders. Maybe the dampener is bad but being on the right side that should have sent gas through the right side exhaust not the left. I'm lost. its parked right now as my garage has another project in it but i plan to get into it more soon. I miss driving it and with the coming of fall id like to get it up and going.

[macgiver]

Sounds like the lower ( small ) O-ring seal to the intake ( vacuum ) side , and I assume "concept Z plus the CUPS " is SIMPLYand probably not engineered well and / or SIMPLY ain't gonna do it in your specific case , and "possible" ,yet NOT guaranteed satisfactory results needing $$$$$$$$$ - a gamble ? Short answer is , can you just "drop back ten yards & punt " - by gettingset of good , new , OEM ( Bosch,Beck/Arnley , etc. ) , cause you have no mention of prior leaks / problems on that note .

[DCaff300ZX]

You will want to use JWT injector adapters if you didn't (pretty sure CZP carries them as most Z32 vendors do), they are the correct option for using the old fuel rail with new style injectors and they also do a little improvement regarding excess fuel accumulations at the injector tip.
Did you replace ALL fuel related items such as fuel pressure regulator, etc.? If not, do so for best results on a 25 year old car.
Do check the O-rings again, they are notorious for problems and problematic to install correctly- I've read of some people who took quite a few tries to get it right, including reports of issues from a few repair shops.
The fuel rail should be fine if no leaks, and I assume you used injectors bought from CZP as well? If not perhaps a revisit checkup of them is in order and also checking to be sure you have the correct size and style.
Oh, and the FSM also has info and help/tests for the fuel system and injectors, it can be your friend for sure.
Hope this helps!