Never dealt firsthand with the Isomac range, but if you're having trouble with the 2 hole tip I doubt the 4 hole tip will help. Generally speaking, the lesser holes the tip has, the easier the microfoam will be to achieve, and visa-versa. The other thing the number of holes has control over is how fast the milk will steam; so the 4 hole tip may be harder to achieve good microfoam but it will get to temperature a lot faster than the 2 hole tip.
How long have you been working with this machine? What's the general technique you're using? Milk? Boiler pressure?