super sucker
A friend had a 25RWHP (and noticeable seat of the pants) increase on a 10-1 360 with mild J's and the Mp557 cam.
But he ran the old Offy port-o-sonic untouched and the MP engine manual says they need plenum work, so maybe the sucker helped the bad distribution??
My 440 likes my home made 1" tapered spacer, no dyno comparison tho, its just crisper in the mid-range under load.
An other bloke I pit for has a 12.9-1 350 :oops: 227cnc heads, .77 roller, eddy intake and 2 UHP750's, that made 583 no spacers and 598 with 2" super suckers.
10 years ago when I still ran a 6 I found far less bog with my home made tapered spacer, comparing it to open spacers or no spacer.
Way over carbed tho, 800cfm on a 271" 6cyl.
Try one and find out :thumrigh:
Godspeed.