No not the hushpower flows, the one's I am talking about are outlaw series race mufflers. They are a true straight-through design. They are in the may issue of 5.0 mustang, I thought it they were in mustang and fast fords.
Ah....I found them. They're more like Dynomax bullet mufflers. Here is the description:
Flowmaster Outlaw Series Muffler said:
The Outlaw Series Mufflers are specifically designed for racing. The round case allows for installation in limited space applications. The design incorporates sound attenuation rings without the need for packing materials. These mufflers provide minimal sound reduction, and are intened primarily for situations where a muffler rule is in effect with no specific decibel requirements. These mufflers are even suitable for some performance diesel applications.
From the description, I think I would only run these with cats. Otherwise, I think they would get you an instant "fix-it" ticket from the fuzz. Also, they appear to only come in 3", 3.5" and 4".