Samsung gas dryer not staying lit. Model DVG50M7450W/A3

I've gone through the guides and replaced quite a few components so far, to include the flame sensor, both coils, the thermistor and the thermostat. The HSI will ignite and the gas valve opens, I get a flame then it goes out within seconds. I get just the slightest whiff of gas. Any suggestions at this point would be most welcome. I don't want to start throwing expensive parts at it like gas valves and main boards without good reason.

If anyone happens to have a schematic so I can test from teh baord without tearing this all apart that'd be great, I haven't been able to find one. Thanks!