I've had pens that were unpleasantly dry to write with using certain inks, inks that performed well in other pens, and these same pens continued to write dry after a bit of nib tweaking, ultrasonic cleaning and use of different converters. What solved my issues with these pens was adding Organics Studio Flo-plus to the troublesome inks.
And boy does it work! My first use of it was about a 1/2% mixture which made a previously unpleasant writing pen and ink combo into an almost unusable wet writer. I now use it at a 1/15-1/20% mixture with excellent results and find it a better option to fiddling with nibs and chasing after a better converter. YMMV