My dad has an MP3. I drove the Mazdaspeed. I have a WRX. Lemme tell yah, I have a stock WRX and it whoops the MP3 and it incredibly faster than the Mazdaspeed. Now I am not very familiar w/ the MazdaSpeed but I believe it runs a very low boost, around 7 psi if I am not mistaking. Now the wrx w/ the simple mods, exhaust, uppipe, engine management puts out 227 whp according to TXS. I think they are exaggerating when they say a slightly modded MazdaSpeed can whoop a stage 2 wrx. I don't think the MSP boost can be increased very much w/o serious mods to the internals. I have been reading up at an MP3 site that also talks about MSP's and the fastest MSP I have seen on the site is still in the 13 secs and that is HEAVILY modded. I am not very sure on your actual questions you posted but I would just like to give my input from somebody who has read about both cars and driven both.