Howdy
I have used both in my M1009 and NOTICED no difference. However, obviously the open plane will flow more air with less restriction just cause it's open. Is it enough to warrant going out and searching/paying for one? IMHO- If you have a split plane, run it. If you only have an EGR manifold and can find an open plan run it.
If you are doing this conversion make sure to clean up the exhaust path as well. Both manifolds can be cleaned/opened up but the drivers side really needs attention due to the egr gate.
1996 Chvy 3500 CCDWLB 6.5 Heathed, NO vac, marine injctrs, ARB bumper, BIG pipe, 3" lift, bright lights, bypass oil system.
1986 Chvy 6.2 M1009 blazer RAM AIR, Headers, Custom interior
2001 Chinook RV, V10 gas
1974 John Deere 1530 diesel tractor
1993 John Deere 455 Diesel lawn mower
1967 GTO, 1989 Honda Transalp
2009 VW Jetta TDI, flashed and piped, 6speed, fun car!
1998 6.5 suburban, stock, daughter's
1993 6.5 3500 CCSWLB GM8, Heathed, big exhaust, gauges, Son's
1984 6.2 ATS turbo 3500, SCDWLB - Son's
3 kids, 1 wife, 1 dog
Gunsmith, Tactics Instructor, Fabricator USMC 87-93 Semper Fi!