After the AFR Plus was installed I think by the time it was run on the dyno I had changed 1 of the 3 exhaust pipes to a TORs but I'm not sure. With your Roadster I would recommend you get the TORs pipes because they give it a little more sound but not excessive. The TORs pipes also eliminate the catalytic converters for better flow. Then add the AFR Plus. For under $1000 you get a really nice improvement. There are good used Roadster TORs pipes available for a good savings. You can find them on this forum or on EBay.
You know we start out wanting to make just little improvements and doing so by not spending too much money. Then you catch the bug. Oh boy what can be done to this motor !