Quote Originally Posted by SG1 View Post
Hmm, I think it does have to be very similar sized piping, remember your stock maf housing slightly reduces in size where the MAF sit inside the piping to speed up the air flow over the maf sensor, the HPD actually is slightly larger in that same area where the MAF sensor sits in the piping(it is honed out slightly where the MAF sensor sits, allowing more air past the maf sensor and slowing the air going past as well), if anything the HPD maf housing could do with being just a little smaller in that area, it is not 30% bigger BUT allows up to 30% more airflow past the MAF sensor tricking it..

Ideally imo the HPD maf housing could do with only allowing 15%-20% or so more airflow past the maf sensor but if you have a chip it can be used to allow more fuel and get a good air fuel mix going and achieve what your aiming for.
Taking this into account I removed my maf housing and measured it up yesterday, the ID has a 2.5mm tapper in it with it being larger on the in going side. So I chucked it in the lathe and removed the taper. To try and slow the airspeed over the maf as I could only get 14psi, with moderate spool up, before getting limp mode. First thing I noticed was how much smoother it is at idle.(my passenger side airbag used to vibrate). I have uped my boost to 16psi now and have had limp mode once since. I'm gunner take another .5mm out on Monday and see how it go's. Is the hpd housing I'd straight through or tapered?