That is a fantastically high dose...you should enjoy the switch to enantiopure (d)-amphetamine, no more heart racing, teeth grinding (l)-amphetamine. The usual Adderall to (d)-amphetamine conversion is 4::3, so 90mg Adderall == 67.7mg dexedrine, or about 4 15mg dexamphetamine SR "spansules" in the morning.