OK I have 2 questions
If a decent driver in a WRX with ONLY an MBC set at 15.5 can run mid 13's(seen the slips to prove it happens)
WHY is a HIGH 12 not possible with a Stage 2 +up pipe and Samcos?
I mean you are talking about like 35+ hp more than just an MBC.
It just seems weird.

It takes a heck of a lot more than 35hp to go from mid 13's to high 12's...

The problem is that the power required to go faster rises at the cube of the speed. The power to gain 1 mph at 100 mph is substanially larger than the power to gain 1 mph at 95 mph.

Using rough figures of a mph of 100 mph for the 13.5 ET and a mph of 104 mph for the 12.99 ET, then you would need to increase your gross power output by about 12.4% .

That corresponds to about 280 HP at the crank for the 13.5 ET and 315 HP for the 12.99 ET, or an increase of 35 HP.

That is exactly what you are estimating as a power gain from those mods. If (and thats a big if) those mods do actually produce that much additional power, it might just be possible to break 12.99 on a perfect day, perfect run, wind at your back etc. condition. In other words it will be very tough but may be possible under ideal conditions.

Those numbers above are assuming the driver is very good and gets the most out of his car. If the mid 13 second run has a trap speed of 101 - 102 mph, then there is no way that driver will get to the high 12's with those mods, because his 12.99 run would require a trap of almost 105 mph or almost 325 HP, which is out of reach based on a 35hp increase from the mods.

Larry