i have to make a desicion soon about exhaust system soon.
-i already have water injected which caused lots of problems last year.
-have another set water walled but they are not in very good condition and i dont want to wasit time in the middle of summer

so i need to buy a new set but: headers style is expensive on the other hand mercstyle manifolds (with risers etc) are 1/3 price.

-is there a huge performance difference between these two?

my engine is blown bb 520 cu.

thnx for help

note: mercstyle means not the stock ones. they look similar but aftermarket. like revolution marines

Cross sectional area of the runners is more important in a blown application than the scavenging headers provide. I have a friend that made more HP with Stainless Marine manifolds than with headers. As long as you use performance manifolds I think the performance difference will be small. In general the headers will probably make a little more HP.