What is a peakboost manifold? I've never heard of that one. They come stock wtih a craptastic callaway manifold (they all crack sooner or later). As far as aftermarket ones goes you have a Thunder, Steedspeed(best one but most costly), MAM, spool (no longer make MAM or spool) or some ebay knock off (soem of these are t3 and wont be a botl on affair)
Which is why its better in my book. You can still get it.. doesnt matter how good something is its worthless if you cant get/use itI would say MAM is by far better than the steedspeed manifold. But the Steed is the only one available today.