yeah, thats a crap ass manifold that someone fabbed up in their garage.... and not very well either... lol.
dave(99b16si) is selling a pretty good manifold and downpipe in the for sale section. it should be plenty for 350whp. i was actually thinking of buying it myself.
my car and goals are about the same as yours. i got the t3/t4 that john(alpha) was talking about. im waiting for the results once the kit is installed, but from what i have heard and read, it is a great turbo for a mild street setup.