FLOWMASTERS!! Are there 3 kinds of 40 series 2 chambers??

[89FHPLX]

I installed 2 chamber 40 series flowmasters. And the car sounds way to load inside the car especially when I get to 2000 RPM's. I dont know if Im correct but are there 3 kinds of 40 series? My friend has 2 chamber also with a H-pipe and his sounds nicer and alot lower.

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89 Police Interceptor
BBK Shorty Headers, K@N Cone Filter,H-pipe no cats, 2 chamber FlowMasters,Under Drive Pullys,14 degree Timing, Short Belt, No Air Silencer, oil cooler, 3.08's, And All Police Package goodies