This is how i diagnosed a VERY similar problem on my '84. I noticed when i'd try to see how fast my car would top out that it'd sputter like the engine quit. Later i noticed because it got worse when i'd try to go a 1/4 mile my car would cut off and/or die around 65 depending on whether i let off the gas or not. I then did the same thing and let it die then checked the fuel filter. If you're not getting enough gas in the mixture (lean jetting) the fuel filter should still be full, it's just the mixture is affected and you're jetting would need to be changed, but i've never heard anyone having a lean enough mixture to have it stall out like it sounds like yours is doing. I noticed my fuel filter was EMPTY after this, so i know my fuel pump isn't delivering enough fuel when i'm romping on it. When i'm just doing normal driving or flooring it for relatively short periods of time it doesn't do it. I ordered a new fuel pump, so i hope it works, but i'm pretty sure that's what it is. Another thing i noticed is after it died w/no fuel in the filter, it'd still start up fairly quickly after it died and if i let off as it was dying it'd still sputter but i could still accelerate lightly after it caught up, so i'm pretty sure my old worn out pump isn't delivering PSI like it used to. Is your fuel pump stock/old? I'm also going to richen the jets in my Holley 600 after i get an air fuel gauge because i noticed mine is running lean also (glazed plugs). Good luck man.
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'84 Mustang 5.0 T5, FMS aluminum radiator & 180* t-stat, 1 5/8 shortys/2.5" duals, '88 GT tail lights and wheels, Holley 4160 4 BBL, FMS smog pump idler
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