No, the adapter will not work with the 18TM. It is a true SB exhaust port. The Traxxas and PiccoMax have the oddball port.
I have looked into making an adapter for a SB, but it is so close in size to a BB port, that the adapter would be paper thin in some spots. Also, a BB exhaust would have a negative affect on the 18TM. The length of the exhaust sytem would theoretically shift the powerband down the RPM scale. You will have more percieved power when you hit the gas, but it will Peter out quickly. At higher RPM's it won't be able to process the air/fuel mixture properly.
The reason the BB pipe works with the PiccoMax is that it has the timing of a BB. It shares specs with another OFNA BB engine, the only differences being, the motor mount flange dimensions, the length of the crank, and the small exhaust port. The SB (traxxas style) exhaust shifts it's powerband up the scale. It makes enough low end torque, that it can overcome the shift in powerband. Picco should have just left the exhaust port alone, or made a port the same dimensions as the RB engines for the Revo. Then you can use the Trinity or RB exhaust's.
PatinumJoe, when I had a PiccoMax, I also chamfered the port for the same reason.