Instead of a split manifold, I went with headers. The set I got (Hedman) are split front-to-rear by design.
The stock exhaust manifold and headpipe is so restrictive that it seems to me that the only benefit from splitting the manifold is to allow a true dual exhaust to be fitted and change the exhaust sound somewhat. I know this is an old rodder's trick, but I don't believe it to be very effective for adding power. Some, yeah...but not nearly what you'd get with headers.
This is just my own opinion and based on my own experience...others may not agree.
