Tioga were just a marketing house really....a branding exercise. They made nothing much themselves early days. Headsets came from tange, pedals form sakae, bars and stems from kalloy etc.
The bigger they got the more they had the makers marks removed!
They also bought up rights for sales of products from other brands. Gradually they moved away from buying in japan and started making lesser quality kit in the far east..Taiwan etc.
The early stuff is good, because its made by the original makers.