4.6l

yea, they are REALLY REALLY hard to see, but they are there. That's pretty much the only true way you can tell if it's a PI, aside from pulling the intake and looking at the ports.

They are above the exhaust mainfold, right below the lip that the valve cover seals on. Front side on the passenger head and rear on the drivers side head.

Does it have plug wires or a coil on plug? If it's a 99, it will have that along with the PI heads. He may have done the PI swap on a '98 engine.