Here are the instructions for super porting the J-Pipe. Do it at you own risk and use all appropriate safety precautions !!
When used on conjunction with the Aerospike Mod they were good for 23 hp during our exhaust shoot out.
I started by making a drill guide for cutting the port pattern in the J-pipe flange. This is a piece of ½” plywood about 8” x 20”. You want the length to help counter the drill press torque. The hole saw is a 1-3/4” bimetal and use the pilot bit for making this hole. You can see where we’re going as the guide for the 1st pipe is on the other end.
I then took the drill apart and placed the cup into the hole.