Hi,
I once had a SimJet 700. It was installed in a Savex L-39 Albatros. From the very first start I had problems with that turbine, so I ended up returning it to the Sim Jet factory. Got a S.J. 3000 instead which is a reliable and steady workhorse.
The 700 was discontinued due to various problems...and from what I hear, the factory has stopped producing model turbines! No service, no spare parts anymore..so my advice is: Buy a Wren 44 Gold or equivalent from another make.

/Pete