My engine started making a loud whining noise at start up but would disappear when it warmed up. The dealer said it was the tensioners and wanted $1300 for the repair. I found this great post and it gave me the confidence to try the repair myself. I bought 2 new tensioners and belts from Autohaus AZ and a $15 32mm wrench at Autozone and did the repair myself in about 90 minutes. The engine sounds like new again. Thanks to E46Fanatics for saving me over a thousand bucks!!!
I ended up getting the mechanical tensioners. I drive the car about 10,000 miles a year so I figure I have another 7 or 8 years before I have to worry about this again.