Painting/polishing engine
Plus you can pick up a braded lines kit. (the stainless mesh that runs over your heater pipes/oil lines/vacuum lines etc) and run that. Looks effective, very tidy, but no performance gain!
If you are handy with the solder and wiring, have a look and make a list of all the different coloured wiring in your car, and buy a bunch of lengths the same colours, and if you are confident enough, you can extend and hide any wiring you can see. Pick up some black loom tubing that you can run the main wires through.
Anything that is alloy, you can take it out and polish it. (plenum chamber, inlet pipes etc). anything faded or crackd/chipped paint, mask up and repaint. Spend a good couple of days on it, you'll be amazed! just make sure you take your time.