The only way I can think of to make a tail pipe work it to weld a piece onto the elbow, take the baffle out and weld the new bit inot the exhaust eg. through the silencer, allow for bigger holes to get more through flow and keep the elbow tight so you can weld it to the silencer further toward the back (tip) of the tail pipe.
I gave-up in disgust, the metal seems to fracture always next to the weld, and bought a sport pipe off e bay.
Although the sporty pipe has never cracked, the finnish (black) is rubbish, it went white-ish and has started rusting already.
I'm saving for a CSC pipe in stainless with the elbows to bolt directly onto the head [-/
The 123 set-up I also found to be lame without the use of the strobe.
Tell me...did you set it with a timing light with the knob to set 10 degrees and then use the TDC mark or a static timing light where one would set it to flash on the 10 degree mark?