Hello Scotty, Love the channel and website! 1991 Ford E 150 conversion van. Excessive chugging…

Hello Scotty,
Love the channel and website!
1991 Ford E 150 conversion van. Excessive chugging under 45 miles per hour. I have done the following:

new distributor assembly and ignition coil (2014)
new distributor (2016)
new fuel filter (2016)
new spark plugs (platinum motorcraft), wires, cap and rotor (2017)

It seems to run a little smoother, less chugging, after a rainstorm when the humidity is lower.
What am I missing? Thanks again

false