I recently remade this video in higher quality. Check it out, it's a lot better and I included a few other things in it as well. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-mJB7RJUp0Y4.html
There's a point in the game where your party is just Ness and Jeff (Don't want to give you or anyone else reading this comment any spoilers) and I recorded those sections first. Mostly because one of Jeff's items, the frozen yogurt machine is only available for that part of the game.
Jeff didn't have PSI, but his genius level intellect left him versatile with making projectile weapons and other gadgets to assist the party if you take the time to build up his IQ. His gadgetry is useful and some of his weapons and items are infinite uses, so it helps with fighting off enemies in the game.