Like I have been saying, the gains I have shown are from improving the whole system. If you leave out any parts it will show less gain for all the parts as THE WHOLE SYSTEM needs to work together. If you improve the whole system and did not have a dual pop, it would kill the gain. If you improve the whole system and left 2.5" downpipes and test pipes it would also kill the gain. The 2.5" full exhaust has 6 PSI backpressure in the downpipe. The 3" expansion downpipe and test pipe have zero to 1/2 PSI in the downpipe. If you added TB's to a system that had 2.5" exhaust from the turbo back, it is not likely the engine would be able to use the extra air volume as the exhaust already has too much backpressure.
