Ok I own a 1996 blazer 4.3 I have no evap system hooked up on my truck it has been disconnected and all lines cut and capped off the truck ran fine for almost a year and It started to go all wired on me it was stalling and sputtering so I had a new fuel pump and spark plugs put in and it ran fine for about 3 days then all I'd a sudden it started stalling any time I wasn't hitting the gas it stutters while I'm driving and at 1 point I had white smoke coming out of the intake and could not figure out what is wrong. But for some reason I dunno why I ended up changing the fuel return line with the vent line on top of the fuel pump and now the truck runs mint. What could be wrong with the motor to do that