hi i have a 2007 mazdaspeed3 and would like to replace the stock struts.i have read so many thing on the mazdaspeed3 forum about which struts to buy it has left me a little confuse. am interested in the bilsteins but don't know which is better the HD or the Sports for my car.I want a direct replacement meaning that you don't have to modify anything but something that is better then stock and will work with my stock springs.can you help? thanks.
The Bilstein Heavy Duty and Sport will both work with your Mazdaspeed 3 without any modifications. The Heavy Duty is a good performance shock that strikes a compromise between sportiness and comfort on the street while the Bilstein Sport is an all out performance shock. Both will be a great improvement over your stock shocks, it just comes down to how much stiffness you are looking for. You can see those here:
2007 Mazdaspeed 3 Performance Struts and Shocks