The rather large hishkits on this 31-year-old G-1159A are called, Hubbard Aviation Technologies QS3s.

They are made up of three parts:

1) an alternating-lobe exhaust nozzle which attenuates low-frequencies into higher frequencies

2) a titanium-core ejector which absorbs the converted higher frequency noise

3) new cascade-style thrust-reversers to accommodate the attached ejector

I actually left a comment about this jet's hushkits on Facebook a couple of weeks back. To see and capture the aircraft for myself was very unexpected, but great. Also, the info about the hushkits comes from an individual who posted an image of the plane on flightaware.