Hi guys

turbine thrust itself is dependent on many factors. Mainly there is ambient temperature and air pressure (=elevation). With a turbine running on a low pressure, hot day at 6000ft ASL you can expect SEVERE thrust losses compared to the same turbine running at sea level on a cool day. Most manufacturers will specify their thrust ratings at ISO....
Apart from that: most manufacturers have a "spread" which is pretty wide. Some will produce high thrust ratings while other (identical) turbines produce less. This is due to the tollerances in parts....you might get a good one, or you might have bad luck and grab a bad one. You can always send it back and request improvement, as well as a test protocol under what conditions the thrust was measured.

Aother thing is static and dynamic thrust. Adding a pipe will cause losses of some sort. The static thust can be increased, though, by allowing more venturi air into the pipe. You can gain up to about 10% by this. However, this slows your exhaust drastically....high end performance is decreased a whole lot (effective thrust is dependent on the difference in velocity of exhaust air and
aircraft velocity....the higher the exhaust velocity, the more thrust will remain at higher airframe speeds). If you are looking for better high end performance then scoot the pipe closer to the turbine. Temps will rise a bit, and static thrust will drop, but on the top end you will be scooting along a lot better. A bypass will also help this effect a bit.

Best regards
Hank