On the bottom left corner of the TB is a idle adjuster for better words. It controls the spacing / how far the throttle cable returns back. Lemme see if I got a picture for you.. but I had the exact same problem as you did.. Look for a little hole, possibly covered up with a cheap aluminum cap. Punch it out with an awl.. and then behind there is a torx screw that controls the position of the return lever.
~700-800 rpms is about normal. mine idled at around 1500 right after the swap, but would go down to normal when in gear. drove around for about 30 miles and parked it overnight, next morning idled at normal even with tranny in park.