Hello Ben,
you need to provide more details in order to get better help.
throttles are a symptom but other resources could be exaustated for example NAT.
try to trace over time
sh proc cpu | inc util
sh proc mem | inc Free
sh ip nat translations
have you configured other security features like ip inspect (CBAC) and so on
if you like you can post a filtered version of your router config removing public ip addresses and username pwds
Hope to help
Giuseppe
Hope to help
Giuseppe