While replacing the timing belt on my Acty, I though it wise to replace both the lower belt idler pulley and the upper belt tensioner pulley. I ordered the parts several months ago and only now got around to doing the job. While the replacement upper tensioner looked identical to the original, the lower idler pulley was made quite a bit differently. The original idler had the bolt hole positioned dead center of the pulley, but the replacement has an offset hole. Actually, I like the replacement set up as it allows you to more easily fine tune the timing belt adjustment. The problem is that when I installed the new idler, it sat closer to the block which caused the timing belt to overhang the outer edge of the idler pulley by at least an 1/8 of an inch. I'm sure this would have caused rapid wear on the new belt, so I found a hardened washer approx 1/8" thick with a proper inner and outer OD and installed it on the bolt between the engine block and the idler. The belt now seems to ride just right. I also had to find a different bolt to hold the lower idler in place as the original one was slightly too long to use with the new pulley. Here's pic showing the new idlers installed and the old lower idler being held under them to illustrate the different design.