Update to this... the fuel trims are still good so the regulator cleaning seems to have worked fine. But the car still has a vibration at idle, enough to shake the side mirrors slightly and get anoying when sitting at the lights. No obvious missfires and it runs fine once moving/under load, just the idle is a bit uneven. Engine compression is good (170 psi +/- 5), plugs/leads are newish and I've checked for vacuum leaks and replaced the intake manifold gasket and
PCV valve (made no difference but good to have done anyway). I'm 99% sure it's not ignition related because problems there show up under load first. So I'm thinking I should just bite the bullet and pull the fuel rail, clean it out, and fit reconditioned injectors. Given how much crap was in the regulator it's likely the injectors are filthy too and causing the uneven idle.
Any tips on removing the rail? Looks like there are some "quick" connectors under the car, do I need a special tool to undo these, or just can I just push back the internal clips with a small screwdriver (like the ones on the filter and pump).