YES the PTU being bad can cause problems on just those two cylinders. And as far as the gas smell, I have had injectors stuck open before and dumping gas in, so the spark is unable to ignite the massive amounts of gas. This resulted in a strong gas smell like you described. Also, if you think about it, if the PTU is causing sparking issues on those two cylinders, it would mean the injector is still injecting gas, but nothing is sparking consistently to burn it,so the plugs would be wet with gas. So I'd do PTU first.
