the difference in effect is likely because the Toprol, being time released, achieves a lower Peak Plasma Concentration than does the metoprolol
So, you might mimic those pharmacokinetics
somewhat by taking the metoprolol with say... a big meal. Fat in a meal slows down transit time even more.
Or have you checked if you can take two half-doses per day, to reduce PPC?
Also, which metoprolol are you taking, succinate or tartrate?