the only thing i would touch in that engine bay is maybe give it a fresh tuneup and make sure it's in great mechanical condition before even thinking performance upgrades.

since your reason for wanting performance upgrades is due to your 70 mile commute, getting passed....i'd suggest just buying a couple new CDs to keep your mind off it. if you're seriously gonna do headers, might as well do a full exhaust with new pipe, cat, muffler, and o2 sensors or it's not gonna be worth it at all - and it's gonna cost a lot of more money than you probably want to spend on it.

if you really want to spend $ on your rig, i'd take everyone's advice and go for lower gears and a traction device. start calling around some local yards (or online) and get yourself a set of factory 4.88 gears for around $500 and then buy online a lockright for under $300 delivered (Aussie is out of the picture since you'd have a V6 diff). so for around $850 after getting the major parts and the misc (parts cleaner, liquid wrench, RTV gasket, gear oil, and beer), you'd be back on the road in 1-2 days and will have a rig that will feel completely new to you - and will give you offroad performance gains that you will ACTUALLY notice.

i'd also suggest ditching the coil spacers and getting the real deal.

if somehow you still have money leftover after whatever upgrades, put it in the bank and save it for when something goes wrong (with your 3slow, hehehe) and you really NEED the money.

btw, i hear yotatech stickers are good for at least 10+HP at the wheels.