Decat down pipe
 

Am looking for a decat down pipe for a 1993 WRX. Must have the sealed ring fitting not the flange fitting. Could do swap have a brand new flange fitting pipe available?

Would also like bit of advice, fitted new bottom end 1000 mile ago and was running perfectly for 800 miles, but after changing oil and filter again engine seems to be pressurising? Had an airlock and a couple of split pipes but am now confused. Think its head problem, engine under warranty so ok but has anybody had similar probs?