1992 350. Truck had absolutely no issues prior. Driving down the road took a turn and it just cut off. Since then whenever I go to crank it it takes a little longer and when it does fire up it revs up and down almost to the point it cuts off, occasionally it will stall. Giving it some throttle does the same thing rpms go up then back to nothing almost stalling out. Replaced the oxygen sensor and the egr valve which it was giving codes for with little improvement. Also seems like I can smell gas. Any ideas what my next move should be?