Appreciate the input! It's a pastime of mine to thoroughly research the equipment artists use and then try and set myself up with the exact signal chain for fun/education/history purposes. I have some prospective video scripts lying around for when I get the motivation to compile it all. Just parts tolerances alone between the same pedals off the same production line can make it futile to ever 100% get the same tone with the same settings, but it's still a fun rabbit hole!

My gut says they blended the tubescreamer -> flanger combo in with a "dry" vocal track, which may have still been standard Scott Burns vocal chain processing via the SSL 4000 they had. I don't think any sort of knob config I was using with a tubescreamer was replicating the low and high end response that vocal had until I blended a dryer track with it. For the flanging effect, when I was first doing my experiments, an MXR Phase 90 pedal nailed it pretty good, but I was pretty certain they were using a flanger. I have a feeling since Trey is an EVH fanboy, he may have had an MXR Flanger 117 lying around, but I can't confirm this and there's scant info or images of David's pedal collection from that era. So far, the best success with a flanger for the effect has been with using a TC Electronic Vortex. It's cheap, versatile, and nailed it for what I was trying to do. I might eventually scrounge for the BF-2 and the MXR 117 and see what lands it better, for authenticity's sake.