I got a 1900 my first time too.. (minimal study)
a 1950 2nd time (LOADS OF STUDY)
and a 2160 last time
I would say hell yeah. of course u can increase. the key is (no matter how cliche this is gonna sound :P) not only prac, but also understanding EVERY SINGLE MISTAKE.
and my 2nd 1950 was mostly cuz i freaked out BIG TIME. I was aiming too high (for an 800 in Math).. the first section I got after the essay was math, I left 2 questions, and u can just imagine the paranoia i was in! I was thinking the whole time of how to come back to that section!
so don't do that.
In my last test, when i was relaxed, I did get that magical 800. and i was surprised cuz i didn't have it in mind while solving.. just did my best (and the test was ridiculously easy :P) I know it's not the legendary 500 points increase, i hope my experience helps XD
btw.. this thread has a 8,988 views to 13 responds.. wooow lol