The problem with the 80e is the very tall first gear, mine runs up to 65 mph in 1st gear with 4.10 gears. If you use a stock converter you're in your low rpm non-power section of your power curve if you have a large camshaft, like mine. A stall converter is highly recommended for this application.
You may be pulling in hot air so the engine is pulling power out of the tune. Did you put a good stall converter in with the 65e or is it stock? History shows that cold days make for great HP and hot days suck.
