according to the service manual if you remove TB from intake manifold you need to replace the TB gasket.
to do that first remove the upper air box and resonators and hoses then 4 bolts for TB after that I put TB aside to access TB gasket without disconnecting cooling lines. then replace gasket.
install just in reverse bolts need to hand tight then torqued to 12Nm.
also, I cleaned TB with an injector cleaner. that's it
and some photos:
