Nice I bet that festa flue! Will be keeping a eye on your front mount progress as would maybe loooking to get a better one for mine in the furture.
I reckon with the 1.8 you will get quite alot of turbo lag using the t3, im sure its been done before. Imo I think you should stay with the ihi as you can get around the same power but much less lag.
Ive just made a manifold to fit a mhi to my golf just in the last stages before i taking it to get mapped. Thats another good turbo to look at, stronger than the ihi's but still can be big power with fast spool up, hoping for 320-350 from my setup.