So fuel pressure prob is same outcome which leaves blocked injector being the only higher risk of 8 vs 4. I would try 8 to see if you could get more power but mikes wife's tales are always wrong so probably not worth it LOL
In my head even with closed loop lambda I still feel smaller injectors can only be better for low speed running etc - whether its worth it on a tuned engine etc who knows for its purpose etc
I have 8 as they injectors were free and not had a problem in the past.