Hi!!
In my case, when I gave the TOEFL test at home i just got 197-230 and I was really scared.But in the real test a person wont be thinking of anything other than the test itself .SO, I feel he will do much better in the real test.As for my real test scores they were between 237-290 and I got a final score of 283.This has convinced me that the powerprep scores are in no way a standard to measure what your real scores are going to be.
Good Luck to all
Regards
Amitha