Very cool thread, I am new here, so new that I do not even have a TDI yet!, waiting for the 2013 passat, I have been a big fan of diesel since 1994 but have never owned a diesel car only ford 3/4 ton trucks, a story for another thread, I would like to share my one and only experience with suspension mods on my 2010 Honda Accord.
One day while traveling on the freeway some road debris popped up at the last second and my reaction with a jerk of the steering wheel was to notice how bad the stock car handled, tires squealed and could not get around the obstacle, I started to do a google search on tire,wheel,suspension mods and after searching a few hours over a couple of weeks I took the plunge, the first thing I did was to change to tein SS coil overs and add a large diameter rear sway bar, handling was improved drastically, since the the car was lowered about 1.4 inches doing this my rear camber was to negative and the stock set up could not compensate for this so an after market adjustable camber kit was installed and at the same time I changed the the wheels and tires, going with the lightest wheels of the size I wanted (18x8.5) and Michelin super sports in 245/40, now handling was improved again and the steering felt more weighted, the last thing I did was to add all the chassis bracing I could find, about 7 pcs. total, this made the steering so tight and responsive that I could not believe the difference, this car could corner as hard as our 2008 535i with a sport package, handling was so precise I could not imagine I was in an Accord!
Fast forward to months later, the car still handles like a dream, I am growing tired of the ride quality (or lack of it!) very stiff compared to stock as you feel every bit of the road, road noise is up as well, the front frame cross bar I installed also bottoms easily on dips/driveways, hard cornering into dips sometimes feels like the rear inside tire lifts as suspension travel is so restricted, a fractional movement of the steering wheel sees you to the next lane fast so you have to be on your toes at freeway speeds.
I had an occasion to avoid an accident once in my newly modified car, I was traveling at about 35 when a pick up suddenly decided to make a left in front of me when I was already entering the intersection, I cranked the wheel to the right and braced for impact, the tires bit hard and the force at which the car turned surprised me as I was able to get out of the way of the front of the truck I cranked the wheel hard back to the left and the car recovered just as fast seeing me through the intersection, in the stock car this is an accident for sure.
To wrap it up, the car is a darter, wherever you point it it goes and fast, is it fun to drive, yes, but at a price, my wife does not like to ride with me as she gets car sick easy in my car, would I do it again, yes and no, not in the same way, I would compromise next time as I would give up some handling to gain comfort and a little more suspension travel, I just figure my darting days are over