[|Erasmus|]

Originally Posted by crAzerk

Your build isn't really going to change much even if he goes ling-infestor, just remember to keep working towards that all-powerful 3/3 Infantry upgrades (most BSGP players stop at 1/1)

What MAY change would be your playstyle - so when you open marine/tank/medivac and you realize he's gone infestor, start doing drops! With infestors he has limited air control and you can terrorize his bases with multi-prong drops and the such and there's nothing much he can do. Snipe queens, kill drones, etc.
I would go as far to say that ling-infestor is an inferior build just because it's not ideal for handling drops. I prefer ling-muta into infestors later on (when marines go 2/2 and above and start getting out of hand)

Drops, and the main change to your unit comp is more tanks. You want a good tank count cause they won't be dead against mutas, and you always need tanks sieged up to cover your marines. Also making a few marauders (since hit squads of 2-3 marauders are wonderful for stimming forward to snipe infestors... also because fast infestor often leads into ultra) is a good idea against that comp.