tomcat tuning question

hello

Recently, I am seeing this message appear in the catalina.out log for one of our AG.
"SEVERE: All threads (150) are currently busy, waiting....".
To fix this problem, should I try to increase the Tomcat maxThreads count ? if so, is there a recommended number?

Also, I read in the documentation on Access Gateway that to accomodate the max number of user sessions one has to make changes to the java memory allocation. (this I already did)
But are there any other tomcat parameters i should be adjusting to get the max performance out of my machine?

thanks in advance
Jim