This shows the design differences and the oem is a work of art but the problem is its weak.
Under stock power applications its the best thing since slice bread but when you start adding
power to it will disintegrate.
The vac is quite a good design and I don't believe the difference will be that substantial compared
to oem but the strength of the mounting point will.
What I like about the vac cover it lets you add a temp sensor to measure the oil temps unlike the
oem cover, when you double or triple the hp of what it was designed for you really need to get serious
with data logging.
I already lost one diff and I'm not about to do it again, only time will tell.
Also the oem cover wont let you run anything over 3.15 gear set as you will have to grind it out and
there really isn't enough meat in there to do it, so you either have to shell out for a 3.85 oem cover
or buy the vac and it will let you run any ratio you like.