There are some key optimizations that can be accomplished with relative ease in Portable Interceptors that are worthwhile to implement in the short term:

1. Enhanced caching in RequestInfo object (an extension to 4393382)
2. Bypass all PI code if there are no interceptors registered
3. Change synchronized ThreadLocal stacks to non-synchronized data type
4. Move clientDelegate and response from RequestInfoImpl to ClientRequestInfoImpl

Any further optimizations should be performed based on profile data.