To the original writer:
The battery in your car may be the incorrect type. I have not seen any other reports of a similar problem with this model here on carsurvey.org or anywhere else. Check with the dealership to be sure.
Your choice of xenon headlamps is the cause of your bulb problems. It is unfair to blame the car for a botched modification that you made. Try using a bulb of a higher wattage (to handle the current flow of the xenon system you installed). But before you do, consult an automotive electrician just to be sure.
What people often do not realise is that a small engine does not mean that the car it is bolted to will be fuel efficient. Efficiency is generally on a curve. There is an optimal engine size for each car that will yield the best results. This 172hp V6 is below that curve. It is hauling a lot of machine around so economy will suffer. That said, 24/19 isn't great, but it's not that bad either.
With regard to that check engine light. Go have that looked at.
Air dam? What air dam?
Engine doesn't think it's warm enough? I doubt this.
Bad CV joints do not "clunk", they "click" repeatedly. And you only hear them when the car is moving and then the wheel turned to either side. Take the car to an alignment shop and have them check the suspension and steering systems.
With all due respect my friend, this car seems to have been fairly reliable. Apart from a few minor niggles, it has never broken down with you. I think you would be better off taking the car to a professional technician instead of nickel and diming the car to death. If you think you will be spared the wrath of Murphy by getting a Subaru, you may be in for a surprise. They have their fair share of issues too. Have a read on here and you will see.
Something to note:
If the car is not getting up to temp, there IS a problem with the cooling system, most likely the thermostat. If this is working properly, then the engine would stay this cold even if you put a pipe in place of the radiator (not gonna happen).
If the car is not getting up to temp, it is never running as efficiently as it should be. These cars aren't gas mileage champs, but I was never disappointed with my mileage.
I also beat the snot out of my Audi, and it took the abuse better than any car I have ever owned. It actually got better gas mileage than my 1.9 L Ford Escort driven in the same manner.