It's most likley nonPI (PowerImproved). The difference is , nonPI will work with your truck intake. PI will not. Intake ports are different on the Heads and Intake. I can't say for sure if the Marquis is non PI. A little extra went into that model. If I were you, I would confirm either way first, -IF you want to use the truck intake (that should be a no brainer IMO).

 

How do I find out whether or not the motor in the truck is PI or non PI?

 

They didnt put a pi 4.6 in the f150 until 2001.

 

Right, but he and I are referring to a Mercury Marquis 1998. Like I said, it's probably non PI as well, I can't confirm that tho. It may of been an interceptor engine in that car back then. The Marquis was an upgrade from the Crown Vic. Some CV's were interceptors as well.

 

IF it's marked it will say "PI" at the back outside of the drivers side head. You would have to look that one up or search it out, I know the info is out there. I can't recall the exact years for that, that particular engine included PI heads, or LY part series heads. That car is a Lincoln.