The highest rear wheel HP I've seen on a ST1100 is 95HP. That bike had a modified air box and a "Factory" brand jet kit. The average is upper 80's to low 90's for RWHP.
You've not stated what kind of ST1100 you have, so OEM jetting will vary pending on, ABS, CA emissions, or 49 State bike.
Your A/F ratio is off the chart. I doubt it's accurate, but close. Putting a sniffer up one muffler(which they probably did) on a dyno run, will get you in the ballpark.
There is a possibility of the carbs being out of tune, sticky float, etc. However, the very first place you'll need to go, is the ignition system. Only takes about an hour to replace the plugs and do all the required resistance checks to make sure your getting full fire in the hole... Please verify that your getting full ignition power before you dig into the carbs.