I’m hoping to get some answers on why my EJ1 won’t start up.

I’ve been having some idle issues when driving where the car idles sometimes at 1-1.5kRPMS and then as high at 2-3kRPMS. It stalled out on me one night driving home, completely dropping in RPMS, and now won’t start up. I’ve replaced the main relay, distributor cap, spark plugs, coils and wires and nothing works. I generate spark at the coil so I’m unsure what it could be. I’m going to try checking the timing belt to see if it jumped a tooth, but I was wondering if anyone had some suggestions on what to test or answers on what it may be?