That is interesting. There are two things that we need to chase down.
First is a fuel pressure issue. Here is a guide that will help plus I attached the info from the manual below that will give the specifics on how to do this on your engine:
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
The next thing is how you checked the flow out of the tail pipe. When you said it was pulling air back in, I suspect you did the dollar bill test? Meaning holding a sheet of paper or a dollar over the tailpipe?
If this is the case and you felt it pulled back in then you have an exhaust valve that is hanging open.
That would explain this issue as well but this test is a little subjective so it may be a good idea to check the fuel pressure as well. Then we can get further into this if it checks out.
Let us know what you find from the info below. Thanks
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Wednesday, September 15th, 2021 AT 8:05 PM