hmmm.. well thats a little difficult to answer man.
Your car went pretty good. It had a FANTASTIC pull through mid revs.
There was the issue I mentioned above about the different runner size, so you will have to take that into concideration.
I have noticed the following from the manifold. Bottom end torque was improved greatly, mid range is about the same, and then top end has a little more pull after 4000rpm then the previous manifold, but she seems to rev easier to 5000rpm.
I still have the standard cam, so once I get a different cam, I reckon it will benifit the car more around the 5500rpm mark. Obviously, to take maximum advantage of this, a good exhaust system is required, which I will also need.
ok, so to cut a long story short. Get a quote for all the things you will need. If you think it is worth the extra bottom end pull, and top end revs, then go for it.
You might be better off getting a higher gear ratio, or a set of extractors for your beast.
CAUTION: Slippery When BOOSTING!