1. O2 is not used during boost. I recommend you disconnect O2 sensor until you fix the issues. It is useless for diagnostics.
2. Wideband telling you 10:1 is super rich. It means you have a boost leak or a maf related issue. Wideband needs to read between 11 and 12 (11.2 to 11.5 is ideal) for pump fuel 93 octane gasoline to run the engine properly at WOT.
3. Smoke test is not a boost leak test. You need to fill the compressor -> engine with 20psi of 'boost' pressure using an air compressor.
make sure to disconnect the crankcase vent tube before doing this. DO NOT PRESSURIZE the crankcase. Recommend pulling out dipstick just in case.
My bet is you have a giant boost leak that does not show up until the plumbing hits 5psi+ of pressure. Or you have a spark blowout issue.
Once you test with actual pressure in the plumbing to 20~ psi and rule out boost leaks, you verify the coils are good, spark plugs are gapped properly 0.032" to 0.028" is fine. DO not go lower than .027" or higher than .035". Make sure you are using the correct plugs NGK copper BKR7ES iirc.
From there it is simple maf -> Ecu -> injectors relationship. The maf placement is important, no closer than 5 to 7" to the turbo. Use a large tube for 300zx sensor. avoid reducers that are not smooth. Look at GReddy Z32 maf tube for sr20det for example. The maf should have a few inches of straight tube on both sides.
The other issue is blow-off valves screw with maf sensors, depending on the type of blow off it may be an issue. Push style BOV are designed to leak near idle from variety of manufacturers and this will cause major issues if you've removed the recirculation tubing.
This is how to properly run a blow off valve on an MAF sr20det.
Notice
1. the blow off is as close as possible to the compressor (turbo).
2. The blow off recirculates AFTER the maf, BEFORE the compressor Inlet
3. The blow off recirc is far away from the maf sensor to avoid disturbing the maf sensor
This is a 450rwhp sr20det that I helped this customer to run properly after tuning it and explaining about the maf situation.