[elhigh]

At work I have an '02 B150 with the 318, same as yours. I haven't made any mods because it's not mine, but I can see lots of places where I'd make mods:

Serious air dam up front. Unfortunately there's not a lot of room for sculpting it to slide the air to the side, but it'll help with the front suspension anyway. You may be able to add a grille block with improved air scooped up from below.

Fair in the rear bumper so it isn't a parachute at the back of the vehicle. It's a little thing but every little bit, right? And it's totally invisible once it's done; nobody'll ever guess you've made a change. Add a couple of drip holes for drainage.

The rear tires are in gigantic buckets just crying for wheel skirts. You could maybe add smoothy discs for the front wheels too. I'd also add wheel pants in front of the rear wheels to break the flow around them, and behind to close it in again smoothly.

You say you can't afford another set of wheels and tires, but you mentioned you're on snows right now? Snows don't last long; they're a softer compound, you're going to need tires regardless pretty soon. When that happens, go as skinny as you can.

I probably haven't told you anything you don't already know.