1995 E-150 lacks power

we bought this van last year, we put in new plugs,wires, cap, air cleaner, checked vacumn it was steady good oil preasure. temp ok. when driven its very slugish until 30-40. it also has a intermitten miss. there is a whistle when acceleratoin but we can't find a leak. I have been told the engine is shot. I think it is an engine electrical problem. I will replace engine if necessary but I don't think it is necessary. I'm stumped. anyone Super Pole

Take a can of carb. cleaner spray along the edges of the intake and all hoses and base of fuel injectors. If you have an air leak the engine will smooth out immediately.