Im new to this site as I just acquired a 1987 F-250 with a 5.8L carb'd 351w. I cleaned her up, had a professional carb rebuild, new wires, plugs, msd, battery, etc. and a good tune. I'm currently getting 11.5 mpg highway (not too bad) and am thinking about upgrading the air filter to a K&N high flow filter. If I do, would it make sense to re-tune?

 

It depends on what you mean by re-tune. Unless you did a lot of adjusting on the carb, I think you'll be fine the way it is.