assuming you already changed engine oil / filter?

You could flush the cooling systems and possibly the power steering fluid and brake fluid...

If you really wanted to, you could consider swapping out your crank shaft position sensor and cam shaft position sensors and it'd be an easy clean your MAF sensor with MAF cleaner spray...

if the car is running well now I wouldnt mess with it...

 

+ Gearbox oil, diff oil and accessory belts and you're good to go.
Have a look at the rotors and pads too and check for play in wheel bearings and bushings.

 

Piston rings

 

 

You a very bad boy.

To the OP - As has been said, fluids and FILTERS are more important than the plugs. (And there's no real reason to change the igniter packs unless needed.) You can change the plugs (since you're going through the trouble of taking them out anyways but while you have them out, read them and note their condition with associated mileage for future reference. Spark plug changes on the VQ - obviously depending on actual usage - have a pretty high interval for change... 60-80k is pretty standard.

And double what I said at top for Travis.

 

but it is a fluid....

 

I'm sorry, but if you have to ask can you really do the maintenance yourself?

 

True. I had to replace the headlight HID fluid pump on my SL. Driving with that wavy light pattern due to the fluid just sloshing around instead of pressurizing properly was unnerving.

True.... but I think it's more important to R&R the muffler bearings instead of piston rings.

And now I've taken this further off course. Bad mod.

 

 

Anything to extend muffler life. Those things are gold!

 

And if you get the titanium muff bearings with the carbon fiber bearing saddles, expect about 12.43 more hp to the pavement! Trust me, I know.