Fuel filter might be constricting fuel flow but if it can get to full RPM early on before it starts building heat on the block I wonder if the coil is going. I had some run issues I was fighting amongst other issues but long story short, I went new distributor, coil, plugs and wires and obviously adjusted timing with that. Rebuilt the carb a year or two ago and it runs like a top every time now. I do replace the fuel filter in the spring too.