Hi,
I've had the same problem with creaking suspension. On a wet day...it will go away. So I suspect a stupid little lubrication issue on the rear sway bar.....soon as the weather get a little warmer( I'm in Canaduh) I will try this myself with some Rustcheck...it's a good lube. Lithium is probably better but the Rustcheck tends to creep into little voids much easier.
I just replaced my spark plugs on 2.5 V6. I used "Bosch Platinum +4". They are about the best that money can buy in my opinion. Mileage and smoother performance was immmediate. I also used some anti sieze compound as this will be critical to removal next time round as they could sieze. I also coated boots and plugs with electrolytic grease to aid in their removal next time and help prevent any possible arcing.
As for the stiff suspension....well I guess your kinda' stuck. I too get complaints, especially from my wife. I want to do something about this as well. You could go with softer springs but that would sacrifice handling. "Munroe Sensimatic" struts might help a little but again, its really the stiff springs and they are set at one stiffness. If you get any other feedback in this regard ...let me know
