Most of the information on the web and in Pina's books suggest replacement of the Bourns filter. But, no, I've not tried replacing that. If I had known-good replacement chips handy I would though!
But I wonder if a SCSI controller or new Bourns filters would in fact be a fix. I say this because I see the "strange artifacts" even if no SCSI drive is connected internally or externally, and even if no ADB or serial devices are connected. I would think the Mac would act up if one of those devices was attached and working through the controller, but unless the Mac polls those chips to see if they are okay, I again cannot see how replacing them would solve the problem.
Nevertheless, you are correct in saying that by not replacing them, you never know if the new parts would in fact be a fix.
Thanks.