The hard truth is yes, any form of VTA (Vent To Atmosphere) dumpvalve will cause any stock EVO to run less than ideally. It's not urban legend, it's simply how EVOs work.
Since I've got more time than I know what to do with, I'll explain also why. :)
The reason why EVOs don't like VTA valves is because the 4G63 engine runs an antiquated MAF sensor setup. What's a MAF sensor? Well, it's that big black contraption that's wired up to the base of your airbox/intake.
MAF systems basically measures air flow and density at the point of intake, which means any air that goes past the MAF is already accounted for by the ECU. This is the reason why EVOs come with diverter valves (the black plastic thingy [metal for the MR and IX] that attaches your UICP to your intake hose). This diverter valve recirculates any excess pressure whenever you slam the throttle plates shut, back into the intake stream, which a) makes sure that the air that has been measured by the MAF remains in the intake circuit and b) helps reduce lag since air that's been compressed is easier to compress again.
When you install one of those WHHOOOOSSHHH VTA valves, you circumvent the ECU's calculations because you release air that's already been accounted for out of the loop. This means that the ECU continues to inject X amount of fuel into the engine because it believes that Y amount of air has been inducted.
This causes several issues. First of which is that everytime you shift under boost, you will run rich. The side effects of running rich is a flamethrower exhaust and easily fouled plugs. The first may be good, depending on your POV but the second definitely is not.
Secondly, depending on your VTA valve design, you may also leak when idling and/or during part throttle driving, leading to either stalling or stumbling, both of which are obviously bad.
Now, you'll certainly have heard of people who claim to run their EVOs with VTA without *any* problems. Unfortunately, this will almost always be a misrepresentation of the truth. EVOs were not designed to run VTA so you will encounter some if not all of the issues I have outlined.
That said, you can learn to drive around most of the problems that a VTA will introduce. Less than ideal, certainly, but if you really want to, you can. You could also install the HKS EIDS to trick your EVO into not stalling but these are all like band aids to a problem that you need not have in the first place.
The only real way to run a VTA properly is if you do a MAP sensor conversion, like what you get with the Power FC.
So to answer your question, what BOV suits a stock EVO most? The stock VIII MR or IX valve.
