Several years ago fuel manufactures started using an anti foaming agent in our store bought fuel. I have tried to make it foam up like it used to and haven't been able to get it to foam. I started hard mounting my tanks and still haven't been able to get it to foam.
It does sound like the carb is adjusted too lean but the EVO engines do very often develop air leaks, often just a loose screw holding the carb or back plate. Fatten the engine up a bit and test it, if it still does it then check all the screws. If all else fails send it into Horizon for repair or replacement. I haven't seen an EVO in a while but they used to put a cap over the low speed needle so it couldn't be adjusted. Good idea but they often came new out of the box out of adjustment so that cap had to be removed to get at the needle.