Scaling a MAF sensor for a new housing 2008 VW GTI FSI

Hello, I just wanted to start off by saying this is a bit more complicated than expected but im having issues being able to correctly scale the maf for this 2008 GTI. The issues i have is that the stock maf housing is oval and the scale matches with that oval of course but the new housing is circular and doing a calculated maf scale does some pretty odd things including torque surging. The other issue I am having with this tune is that i get knock at lower load cruising but not anywhere else in the rpm ranges only less than 3000 rpm and under 50 engine load.

Thanks for your replies.

An oval housing does make things a little more tricky but you can still work out the cross sectional area by multiplying the major radius by the minor radius and then multiplying the result by pi. Use this and the cross sectional area of the new round housing to work out an initial multiplication factor you can apply to the scaling table. From here you can fine tune the scaling as explained in the Practical Reflash Tuning course.