Car he bought was mine, mechanically it ran perfectly and the new owner has driven it to and from geelong - melbourne a few times since.
I drove the car daily everyday till he took the keys off my hand. I have also been driving the car for a good 4-5 weeks in standard form day to day, to and from work without any hiccups. Alot of people know the history of this car more so in melbs15 not NS. Most will know I'm extremely pedantic in taking care of it and go to great lengths to maintain it.
I can also confirm Mop has pretty much worked on my car from day one of my ownership back in 2006 till recently.
I don't think the buyer is blaming anyone, all he wants is a solution / help to get his new toy back on the road!
To those that don't know the full history of the car please stop suggesting things as a guess or speculation.
Dude already told ya it is very unlikely being an ECU issue... you really need a different mechanic that works on imports / s15s regularly over there in geelong to look at it.
The injectors SHOULD work like new as it has only done approx 60k kms... as I had nismo injectors in it previously. I strongly suspect it is something to do with the fuel used when the tank was literally empty, pouring unknown "unleaded" that is obviously not recommended and also more than 2 weeks old bad batch of fuel happens and is very rare but when it sits around in a jerry can for a few weeks it can go off and lose even more octane.
I do however believe with the symptoms it might be something to do with the injectors.
Try to get some injector cleaner in the new fresh batch of fuel.
Carby cleaner on the throttle body
Contact cleaner on the IACV / AFM
Stay away from champion poo plugs and get some NGK's I've religiously used BKR6E variants every 5k kms.
I would also suspect maybe the O2 sensor might have an issue if there was a bad batch of fuel that flooded the chambers, but leave that a bit further down the track.
You really need to start with the basics then start diving in deeper.
Cranking issue? Maybe the starter motor is on its way out but if the engine is flooded cranking issues are fairly normal!
The Optima Yellow top battery in the car gives it plenty of Cold Cranking Amps.
Since the fuel has been drained and car re-started are the cylinders re-flooding? Is it only 2 of the 4? try moving the injectors around and see if the corresponding cylinders flood with the same injectors!
I can also vouch for PhoneixGSR's work shop and know he will take care of your car.
Abit more history on what's on the car for you Marinko in the current form, from when I sold it to ya:
Nippon Denso Fuel Pump
Trust (Greddy) Easy Cams 254in 10.5mm lift 264ex 10.5mm lift factory cam gears
Tomei Rocker Arm Stoppers
Nismo Supper Copper Mix Clutch
Nismo Reinforced Pivot
Nismo Gearbox mount
Nismo radiator cap
Nismo Engine oil cap
Nismo tinted side indicators
Sydney Kid Eibach Bilsten Coilovers
Noltec Camber tops
Whiteline Sway Bars front & rear
Whiteline Pineapple Kit
Whiteline Castor kit
Cusco brake cylinder stopper
ADR Braided Brake lines
Braided turbo lines
Genuine CF Cluster Surround
Genuine Chrome Cluster Surround
Custom Carbon Fiber instrument cluster surround
Blitz MD Meter Boost Gauge
JDM S15 S-Wheel
Kaixen 6000K HID's
Mtec White LED Parkers
Optima Yellow Top Battery D35
Pioneer HU DEH-8850mp
JL Audio VR600CSI Component Splits ~ Front
JL Audio TR600CXI Coaxial ~ Rear
Cadence 4ch Amp
Gold Stinger Battery Terminals + Cover