92 f150 plugged converter?

I have owned this truck since it was new. It now has 161,252 miles on it. At 121.450 miles, I rebuilt the engine. .030 pistons, rebuilt heads, ground crank. It started acting funny recently, like no acceleration when it is warm out. After a rain, and it cools down. it runs OK. I replaced the MAP sensor due to the code saying it was out of range. The vacuum is about 19". I have disconnected all vacuum lines except the MAP ;ine, and the vacuum stays the same. I get an air rushing sound when accelerating, but no good acceleration. The trans also has harsher shifts. I change the tranny fluid and filter every 30,000 miles. I am wondering about a partially plugged converter. What symptoms would that cause?

Thanks for the help. Ken