I run my Plus 8 at 20psi all round but it's on 205x55x16 so a bit different. I use to run the 4/4 Sport at 22psi all round and that suited it on Toyo tyres.
2009 4/4 Sport Henrietta 1999 Indigo Blue +8 2009 4/4 Sport Green prev 1993 Con Green +8 prev