Static electricity: Unique to Vinyl Systems?

Did you also replace tonearm? You'll need to check ground path if there's continuity.

1) I would not trust any aftermaket powercords, but that's just me I guess. My background and current work as live sound tech is what really pulls me off any fancy stuff like that especially when spoken about high gain devices. I would hate to attack anyone who does like aftermarket PCs here because there had been gazillion posts, but regardless, try to use stock power instead and see if it goes away.

2) I'd also try to avoid any MC step ups as there's theoretically none's better than direct to SUT-free phonostage. If you can afford SUT, either you can afford better and higher out MC or MM cartridge and you get your sound set up substantially better and who knows maybe your SUT a-bit 'unhappy' where it is where could be numerous reasons and impedance mismatch isn't the first or last.

3) Power ground isolation. I've seen many home wireing where newtral is instead of ground or ground isn't connected at all

analogue domain has the highest gain and therefore more susceptible to RFI or static electricity. Also forgot to mention to check tubes if you have them.
how often is your pops? i get them once in blue moon. most of the time i keep my preamp on mute and only engage phonostage when i play records which may be another tip for avoiding those lousy pops.

Definitely it's not RFI, but static charges that haven't been filtered or choked. Poor caps or weak caps, poor circuit engineering is the cause.
I get them once in a while becouse I need to recap my full function preamp.