I know this post is 5 years old now but maybe this will help someone looking to solve the "clunking" issue.
Disclaimer: I'm not advertising this as "the" solution but definitely a possible problem to eliminate when trying to diagnose.
Summary to save you the reading: Check the upper strut mounts
A few years ago I picked up a B5 A4 that had been used and abused. The kid before me threw Racelands Ultimo coils on it to which I later found he also did a horrible job on the install. I lived within walking distance of my job at the time so I put maybe 25 miles on it per week. After about a month of hearing this terrible clunking noise and the front end bouncing like a GD covered wagon (which I blamed on the likely blown Racelands) I said enough is enough and decided on new coils. At the time I also had a bagged S5 in the garage that consumed most of my car budget so I wasn't looking to sink a lot of money into coils on my daily that I really just wanted to sit a little lower (OEM+ look). I also didn't demand perfection in the performance department in a DD. After a bit of research, I ended up going with ST. I had my reservations, but it seemed like a good bang for buck option with reasonable hope that they would be an improvement on the Racelands. A few days later my ECS box showed up and there they were. I spent the following weekend in the garage leisurely replacing each corner accompanied by the dog, a half case of Rolling Rock, and (old) Top Gear playing on the TV in background. (In hindsight I would have spent more time going over the car to make sure the previous owner didn't f&#* up anything else, but I didn't) I wrapped up my install, backed the car out, and I was off. Within the first 500ft I heard the same clunk and felt almost the exact same bounce. Needless to say, I was PISSED. It was little to no improvement and I was now out $800ish and a rare totally free weekend to spend in the garage. On Monday I called ST and described the issue. Their customer service was great to deal with, we went through a few things and determined that coils were probably fine and they were just softer than I was expecting (I think I had failed to accurately describe just how bouncy the front end was). After another week or two of bouncing down the road clunking away, I had enough and decided to rip the front corners apart again... this time paying attention to everything as I went. As soon as I got the first corner back out of the the car I saw it... the upper strut mount. The center of the mount had been shaved away opening it to about two to three times the size of the piston. Ordered new mounts, threw them in... problem solved. No more clunk, no more bounce.
Side note, I was actually impressed by the ST coils for the price. I can't say they'd be my first choice, but in my situation on a non slammed daily driver... they were pretty much perfect for less than $1000.
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