The TS-790 doesn't behalf as expected for speeds over 700 LPM. In order to eliminate this limit just remove the condenser C221 in the STBY unit. STBY (A) (X59-3480-00 (G)). This is a very little SMD conderser. After being removed the TS-790 will work pretty well at higher speed (it has been tested up to 1200 LPM).
I want to thank Enrique EA2LY/4 who kindly passed to me this information.
Gabriel EA6VQ @EA6URP.EAPM.ESP.EU
Click here to read more mods for the TS-790