No for a couple reasons...
First, they require different water. A figure 8 should really only go up to an SG of 1.005, while an adult GSP needs at least 1.010, and can live in up to full marine conditions. Secondly, the GSP, from my experience, would be the more aggressive of the two, and you would have at least one torn up puffer.
If you're trying to think of things to keep either of these with, I've kept my figure 8 with knight gobies and a molly for over a year so far, with no problems. If the tank is large enough, you can also keep figure 8s with other figure 8s.
As for the GSP, I have a fairly young GSP in with young monos. The combination seems fine so far, but it is something I'm going to have to keep an eye on as they grow.