My first thought would have been a vacuum leak too but when you say no codes then I start thinking elseware. Usually the car will throw a code for a vacuum leak or a lean code. Maybe if it is small enough to affect only at idle and not higher RPM's the computer doesn't pick it up though? I'm running about the same setup as you. 6spd, Catless, Full Miltek downpipes and exhaust, Rebuilt Scroll Turbos, SAI system deleted, Nubcake tune. I have Apikol transmission mounts (Poly) and Stern engine mounts with a 034 Density line front snub mount and I get a slightly increased vibration at idle but it's pretty smooth overall, hardly noticeable. Since you're getting no codes, maybe it's time to do a complete log, either Vagcom 3, 31, 115 I think and see if it all matches up or doing Nubcakes ME7 logger you get a lot more channels but trying to interpret what they all are is difficult.