When you say the max instances, are you talking about the FCGI part in the vhosts files?
I'am talking about the mpm settings in the apache2.conf file.
But you can take a look in the vhost file as well, be default the values in the vhost file should be:
# IdleTimeout n (3600 seconds)
# An idle fastcgi application will be terminated after IdleTimeout seconds.
# ProcessLifeTime n (7200 seconds)
# A fastcgi application will be terminated if lifetime expired, even no error is detected.
# MaxProcessCount n (1000)
# The max count of total fastcgi process count.
# MaxProcessCount 1000
# DefaultMinClassProcessCount n (3)
# The minimum number of fastcgi application instances for any one fastcgi application.
# Idle fastcgi will not be killed if their count is less than n
# Set this to 0, and tweak IdleTimeout
# DefaultMaxClassProcessCount n (100)
# The maximum number of fastcgi application instances allowed to run for
# particular one fastcgi application.
# IPCConnectTimeout n (3 seconds)
# The connect timeout to a fastcgi application.
# IPCCommTimeout n (20 seconds)
# The communication timeout to a fastcgi application. Please increase this
# value if your CGI have a slow initialization or slow respond.
# BusyTimeout n (300 seconds)
# A fastcgi application will be terminated if handing a single request
# longer than busy timeout.
you can e.g. tune the MaxProcessCount and DefaultMaxClassProcessCount parameters.