IIS V8 is really slow on certain type of pages

Hi,

I am doing a cloud migration project and during testing discovered a problem we also had in production.

I was using jmeter to load test the new website and if I hit the website with light pages, it perfroms really well, the web server CPU is high and it is responsive.  When I hit the website with heavy pages, the CPU usage is around 10% and it gets really slow.  The server does not consume most of the memory too.  This eliminates the lack of memory theory.  Hard drive and network interface are not the bottlenecks either.  New relic shows some Request Queuing  and unusually high .Net CLR (up to 10 seconds).

Here is a screenshot:

https://www.flickr.com/photos/roustam/14415948110/

I was wondering if it is a scalability problem of IIS or there is some thread memory limit, which makes it slow for bigger pages?

This is what we are running:

Windows Server 2012 Version 6.2 (Build 9200)
IIS Version 8.0.9200.16384

Thanks.