Hi,
Meanwhile you go through the links and suggestions provided by Hal, I want to share my experience where I had similar issue of late responding APM.
So could you please let us know something about your architecture and deployment of CA APM like how many clusters, how many agents, metric count etc
Because over-crowding of agents resulted for me this kind of issue. [including clamping for me]. Bdw which version are you using ?
Also could you please check the network health between your Wily EM\MOM and the client.
Last but not the least, if this is the case with thick client only, try to increase the heap assign to workstation in IntroscopeWorkstationproperties file and share the difference.
Hope it helps.
Regards,
Vaibhav