Sorry, I dont have IMAQ installed, so I cannot test.
One thing to look out for when doing benchmarks to compare versions (You did not say if you actually did that.):
Make absolutely sure that you save the entire herarchy of your project in the new version before doing any benchmarks. A freshly converted, but not yet saved VI or subVI will be significantly slower and use more memory until everything is saved in the new version. You did not write if you actually did that.