Please help, trying to diagnose issue

[Sugarwaterpurple]

Not sure if this is the appropriate section to post this, if not mods please move

Just picked up an S13 Sr20det a few days ago, was driving the car around last night (about 60 degrees out) when it starting having an issue. Was cruising fine in 2-3 gear at about 45 MPH when suddenly the car became a bit less responsive and engine began to stutter under throttle , AFR's dropped straight to 10.0 constant regardless of gear/throttle input and A LOT of black smoke started coming out the exhaust. Threw the car into neutral and immediately the RPMs dropped to 0 & car shut off .

Pulled over and started the car back up (hesitated to crank up needed to give it some gas), it ran fine for about 2 or 3 minutes but then the same thing started happening again, had to blip the throttle when in neutral to keep the engine from shutting off. My 1st thought is an ignition issue . Any feedback would be greatly appreciated !

Note: car is on stock sr20det maf sensor with 800cc injectors but on the tune I have them set as if they were 600 on the nismotronic to keep the car very rich since I haven't been able to convert to map yet & don't want to exceed the 280 hp or so that this maf can handle. car has a walbro 450 and a rep HKS BOV . for some reason previous owner had the ignition fully advanced on the distributor and I've left it as is so far) on idle the car runs very lean (AFR off the chart) but very rich when driving normally. right before parking the car I did go WOT for a sec and it got into boost fine