I started working through the OG11 about 4 months ago, but it hasn't been until about six weeks ago that I started taking the studying seriously, after I registered to take the GMAT on November 24th. At this point, I've gone through nearly the entire OG11. My practice exam scores so far:

GMATPrep1: 730 (I didn't note the raw scores)
800Score1: 710 (39Q, 48V)
800Score2: 670 (37Q, 46V)
800Score3: 710 (37Q, 49V)

I'm finding that the quantitative sections of the 800Score exams seem much harder than what I encountered in GMATPrep1 and the OG11, which supposedly approximate the real GMAT. Also, the quantitative questions in the 800Score exams seem more obscure and time consuming than.

Has anyone had a similar experience with 800Score?

Is it the general consensus that aside from GMATPrep, MGMAT is the best approximate of the real GMAT?

Given the fact that I only have three weeks until test day, any ideas on how I can boost my quantitative score? I have a B.S. in engineering, so math is supposed to be my strong suit, but these 800Score exams show a huge disparity between the quantitative and verbal scores, with the quantitative score being much lower, which is definitely affecting my confidence level right now.