To bump an old thread, I just tried this combo yesterday.
2 doses of 4-fa adding up to roughly 300mg (2 x 150mg caps 3 hours apart) and then 4-5mg of 2c-i snorted.
the 2c-i seemed incredibly strong and visual, stronger than a 20mg oral dose of 2c-b i had done the day before, as the 4-fa wore off I also started to trip harder and after i smoked a few bowls of weed i was tripping too hard and had to take some benzos.