No, I do NOT accept that the Germans could get the gas chamber as described by Wiernik to work. They no doubt COULD have built a functional gas chamber but the alleged gas chamber described by Wiernik et al. is an impossibility. Wiernik describes the gas chamber as having three (3) chambers or rooms. Each chamber had an inflow pipe that was connected to the IC engine. A "system of pipes that circulated gas from the engine to various chambers" is either a figment of your imagination or a hallucination. Your claim that the Germans had some method for dealing with the pressure and only ran the engine for a few minutes is spurious. The witnesses uniformly claim that the engine ran for 20-30 minutes. Neither does it explain how the air was pumped out of the gas chamber as described by the Soviets, Bomba and Rajchman.You accept that the Germans could get the gas chambers to work and that Wiernik describes a system of pipes that circulated gas from the engine to various chambers, with hermetic seals to stop leaks from the doors and vent caps.
Your objection is that the Germans could not have figured out how to deal with the pressure caused by pumping in the exhaust gas. I would suggest it was dealt with by the system of pipes and that the engine was only run for a few minutes, enough to raise the CO level to fatal.
Just as Wiernik's depiction of the graves and stockpiles of ex in his model proves that he didn't see any such graves at Treblinka, his description of the alleged gas chambers proves that he didn't see any gas chambers at Treblinka.
No cremains, no graves, no holyhoax. Finito. End of story.