I bought the complete build books for my 1988 lx Convertible. When checking the vin stats I have on the vin plate it has a E code for the engine. In the Ford build book it is listed as a 5.0 EFI HO (plus). Can anyone tell me what the (plus) is. This is in the 1988 Ford car shop manual. Volume D Powertrain. This is from the Training and Publications Department of Ford Motor Company