UNX based reports and universe are slow ?

Hi,  We have recently migrated to our Universe from UNV to UNX.

We see that reports and Universe are very sluggish and does not even open(just open and not running them) in the same configurations where same UNV based reports are loading quickly.  

Does UNX reports/univese requires more memory compared to UNV ?

Are there any performance tuning specifically required UNX ?

Thanks

-Siva