delslow45

second time i'm having this issue, still can't find the issue, just lookn for some helpful ideas
first, did a mini-me on my 95 del sol s(5spd conversion) about a year or two ago
everything went smoothly, did the z6 head on a d15 block, new gaskets, cap, rotor, plugs, and wires
car fired first start, everything ran smoothly. a few weeks later the car decided it didn't wanna start
had spark, compression, fuel pressure and all the other ingredients needed to turn a motor. car cranked, and just refused to start
tinkered for hours with no luck, went inside, came back out a couple hours later, the car started and ran fine
starting issue came and went for the next couple months, some days the car would start and run just fine, others it would crank and crank without ever firing, just ran only when it wanted to. some days it would fire, run for hours, then i'd shut it off for a minute or two, and it'd refuse to start again
issue magically went away eventually, then came back for one day about 6 months later, then disappeared again after that. the car has been good to me ever since, zero issue whatsoever. never figured out the issue tho

now, just bought a 97 4dr ex(auto) for my sister with a blown headgasket
did the headgasket, water pump, timing belt, and full tune up last week
car started up fine, ran okay, but misfired like crazy and gave no throttle response until about 1400-1600 rpms
drove it about 5 miles home with no real issues other than the misfire at low revs
had a cel for a bad o2 sensor, no big deal
just got back from vacation today, grabbed an o2 sensor on the way back home
replaced the o2 sensor, started the car(ran fine), pulled it outta the garage and the car died in the street at the end of my driveway
once again, car cranks, has spark and fuel pressure(haven't checked compression yet)
basically i'm in the same exact situation as i had before

i may be missing something simple or maybe i'm just completely incompetant(sure hope not haha), but i'm completely stumped on the issue
i've triple checked my work on both cars
everything's connected, checked, double checked, and then rechecked the timing, car has power, gas, everything is copesetic, car just doesn't wanna start
i have a friend who encountered the same issue after doing a b16 swap into his eg and never was able to figure it out either, he wound up parting his car out
i've read endless threads on similar issues, every possible solution i've read has been checked and tried, i've posted on this back when i had the issue with my del sol, just haven't gotten a sensible answer
any help or ideas are greatly appreciated