I attempted the GAPS intro/diet but it didn't seem to do anything for me, so I eventually went a different route to heal my IBS/possible leaky gut/digestive issues. I personally found the intro phase (and even the full diet) to be too limiting, but I'd already done over a year's worth of elimination diets with no positive outcome. I eventually found out that for me, making an improvement wasn't about eliminating even more foods from my already strict paleo diet, but trading out the high insoluble fiber veggies for more starches and sugars, using bone broth, supplementing with L-glutamine, eating smaller meals, and improving sleep and stress. I'm sure there are others out there who used the GAPS diet with great effect, but it was a bust for me.
I found this article by Chris Kresser to be really interesting; he discusses the GAPS diet, specifically how to know whether it's helping or not.
Answers to your burning questions about digestion