Is it preferred to use a Vac/Boost gauge? It must be easier to read a gauge that only has boost since it occupies all of the sweep rather than only 50-60%. What are your opinions? What are the advantages of being able to read vacuum?

You want to be able to read vacuum. It's important to see if you have a leak among other things.

Wouldn't boost tell you if a leak existed?

go with vacuum and boost

Any particular reason?

Also I've always wanted to know how to pronounce Defi. Is it, dee-fy or deaf-ee?

Boost will tell you if your MBC\EBC is good

But wouldn't it also indicate if you have a leak by not reaching full boost? In fact I would imagine boost would give you a better indication of a leak than vacuum. I don't suspect there is -20psi of vac usually.

As of right now, a pure boost gauge makes more sense to me than a vac/boost.

Mine pulls 20 psi vac which reassures me there are no vac leaks.......the point being made that you can turn your boost controller up to compensate for the vac leak. I have a 30vac/30boost and I don't think I will ever run higher that either one of those numbers. Why not go ahead and have the best of both worlds?

You need vacum for this very reason.

I think I understand now. Boost only gauges would definately show a leak but it could be from a hose, diverter valve, or a boost controller (if installed). A vac gauge would narrow it down to a plumbing problem since the DV and controller don't play a part in vac conditions. Thanks for the tip. The reason I liked the idea of a boost only gauge is the whole sweep is boost thus easier to see when driving.

Anyone know the correct pronounciation of Defi? dee-fy or deaf-ee?