My uneductaed guess is that the average non-SVT will see very limited gains (5 hp or less) from an SVT manifold no matter how big it's hogged out. I've dyno'd my car with and without an SVT uppper intake, and in both cases I got power plummeting after 6000 rpms. Even though I cant compare the absolute value of the 2 different dynos, the fact that power still plummeted at the same rpm with and without the SVT upper indicates to me that there is another more significant obstruction to airflow above 6k rpms that shuts us down (cams, lower intake?)
This is my dyno with the SVT upper intake on:
Dyno with SVT upper This is my older dyno without the SVT upper:
1st dyno without SVT upper Note these were done at two different dyno shops years apart - the only thing I think is significant is that they both show power dropping off after 6k where the SVT upper should support power right out to 7000 rpms and beyond...
my humble .02
(I would also think that maybe as the primary runner ports get bigger you might see a small corresponding decrease in the low end tq as the air velocity through the upper would go down, and our low end tq is all about cylinder filling)
