Tanio Koba has added news of their own upgrade parts for the Tokyo Marui Hi Cap 5.1 pistol (this pistol certainly seems popular with the custom part houses).
The set includes a replacement compensator, Barsto marked barrel , inner barrel set, valve upgrade and reinforced internals. These new parts are hitting the Japanese stockists at the moment, so should be available at your favourite retailer very shortly
There’s also details of new slides coming from them too, but at the moment there’s just an "under construction" style page online. It’s worth having a look though, as there’s a photo of what the slides will look like.