I am considering getting MTM chip for the car. How does one get around the issue with the immobilzer or is it not an issue at all. And also, from what I understand, I have to use a VAG to clear some kind of codes after the ECU is switched, is that correct? Again, TIA.

Can't tell you for sure about MTM. However, with the APR chip there were no such problems. No immobilizer issues & no fault codes after re-installing the ECU. I think all the chip makers have found ways around the immobilizer problem, otherwise they couldn't market the chips for newer models.