I don't have a modular engine but I'm a Powerdyne user, I had the belt driven blower (BD-11A) and now have their gear driven version, the XB-1. I will tell you, from my experience only, that I had no problems with my BD-11A in the 6,000 miles that I used it. I had 40+ dyno runs, about 10 quarter mile passes, and many, many street blasts. The blower was dead quiet. The reason I upgraded is because the BD-11A is an entry level blower with no room to grow and I wanted more reliable boost. It's capable of 800cfm and about 9lbs of boost. Pushing it beyond 9lbs could put the internal belt at risk of breaking. Though some have broken their internal belt with less. Don't get me wrong though, it can make really good power. It's just easier making good power with a more powerful blower like the S-trim or XB-1.
In my opinion, unless Powerdyne makes the XB-1 for your car (I don't think they do right now) I would go for the SQ S-trim. A friend of mine has one and it's pretty damn quiet. Not as quiet as my BD-11 but more so than my XB-1. The biggest thing though is the S-trim can grow with your car. Vortech is known for having reliable blowers while you never know what you are going to get with the BD-11 belt driven series. Some, like mine, seem to last while others don't last three months.
By the way, I bought my XB-1 from Tyler at Proficient and he really knows his stuff. I would recommend him any day of the week. Good luck.
