Hello,
I'm Matt and I specialize in performance optimization projects. You can easily confirm that by looking at my past projects, most of them are related to MySQL/PHP/Linux optimization. Now, about issues Your're seeing... It's hard to predict based on just configuration files and graphs what is cause of the problem. Some variables might have values that aren't optimal for all three components - MySQL, PHP and Lighttpd, but that heavily depends on amount of processed data, generated pages etc. For example it might be an issue with access to mutexes in PHP (if You're using APC), limit of open files on Linux level, limit of open connections (again, on Linux), Chrome/Firefox settings regarding limit of connections per host name (which happens to be 6) and so on. We can pretty much exclude issue on line MySQL Server - I/O as if it was an issue We would still see higher thread count. I'm sure that I will be able to find cause of the issue quickly by testing system components in isolation (Browsers-Lighttpd, Lighttpd-MySQL, MySQL - system) and checking where the bottleneck is. Of course it's also possible that relatively low performance of the system is sum of small factors that add up - in that case I should also be able to improve its performance.
I'm sorry that I can't write more but bid proposals have character count limit. Please let me know if You have any questions - I will be happy to answer them all.
Thanks for considering my bid,
Matt