Engine Feels Flat

I Have A 96 4.3 For My Wife But The Pedal Feels Hard To Push To Get It Going I Don't Mean Its The Linkage. Everyone Tells Me To Get A Tune Up But It Doesn't Miss Abeat Its Just Slow I Thought Maybe The Cam Lobes Were Worn Down But Lately I Wonder If The Timing Isn't Advancing I Ran A Vacum Test For A Plugged Converter But There Was 17 Lbs Vacum I Would Think That Was Fine

well since nobody else will answer, my reply probally ain't right but tis something, check the fuel system, lines, pump, filter, look for kinks and all what not. but like i said i is probally wrong