with headers, you dont need a downpipe. the downpipe only fits with manifolds, which is what the stock exhaust has. the headers will go straight from the block to the cat back, or in fron of the cat, i dont really remember. if you want a downpipe, get a PLOG also
https://www.zzperformance.com/grand_...=208&catid=110
get them uncoated, i heard the coating is crap anyway. either both of those or headers.