Oh they run suPHP, ask them to check if the server logs for that are not large, so if they have pruned them.
Not doing as such will result in massive performance loss.
Next to that, suPHP is not exactly known for it's super optimized performance, it's a resource hog on a server. It's very secure, but a resource hog.
A better environment would be something like mpm_event with FCGID. Even a Apache DSO with mpm_prefork runs faster than suPHP, heh.