An Apache httpd performance tuning gotcha

In the process of tuning a server for a client, I was playing with the MaxClients directive. The normal finessing of having plenty of clients balanced by having enough CPU and memory to handle them. I couldn't get my configuration changes to work how I wanted and kept reaching my MaxClients within minutes, and was wondering if I had changed the wrong stanza, i.e. threaded rather than prefork even though I was 100% sure it was running prefork...

But then, looking around the configuration directories, namely /etc/httpd/conf.d and found a file called swtune.conf which apparently is an artifact of the Virtuozzo/VZ VPS installs. This file had defined it's own stanzas for prefork and threaded that were over riding anything I set in httpd.conf! Removing them meant my settings took affect and the net effect was a happier server!