Do a compression check.
Make sure TPS is set in idle mode, This guy has a pretty nice video. I get it's for a z32tt but I had a rb20det and pretty sure I remember the process being the same:
https://www.youtube.com/watch?v=i37NIF_SUCQ&t=236s
Also make sure your spark signal you are getting for cylinder 1 is correct.
For the Z32 you run off the PTU (ignitor) there is a lengthenged cable that you put the timing light guy around. On the rb20, I don't remember, but on my rb20 I set timing off cylinder 1, not the ptu/ignitor, it was harder this way to get a good signal.. I do remember the rb20 igntor sucks and it's best to upgrade to j30 ignitore or something. I upgrade mine.
Your problem could be a boost leak causing it to fall on it's face with improper timing.
Are you sure your injectors/fuel filter is good, correct spark plugs and proper gap? all good coils (bad could cause miss rb20 ones go bad a lot, run no coil pack cover to keep them cooler, all this little shit unfortunately adds up.