The guy I purchased it from said he was told it was gutted at some point so I had a good look at it and can see all the new welding. It's on the loud side so I'd say it was done.
I've never heard of this and I used to race in the ice, grass drags (MSDRA) and I doubt it does anything for performance except save a small amount of weight.
I'd still like to know what's being removed inside, flat pieces of steel, cylindrical, any perforation in what's being removed? Anyone have any pix or make a sketch and post it would be appreciated.
Is the o.p still on here and did you go ahead with it?