We run George's 1 1/2" OD headers on our 2.7 short stroke engine. When I asked Woods about this, he said he uses this size all the way up to 3 liter. Unlike our diesel, where we run a 4" open exhaust, you need some back pressure, especially if you are going to use the car on the street. We cannot run the stinger mufflers on the street, as there was not enough back pressure during transition. Ok if you are going flat out. We were able to tune a flat spot out by adding backpressure.
