I took my truck for a drive today and i noticed at 2500 rpm it started to stumble and blow white smoke. At idle and driving around it runs fine just when I get her above that rpm it all goes bad. Any ideas? The truck has not been driven alot in the past year at all and I'm trying to get it roadable again. It starts a bit rough in the morning about an 8 second crank but after that it is fine it starts right up and my glow plugs are bad.