I have an 04 AT that I put straight pipes put on about two months ago. For a week now my car won't start. It will crank but not start. It started today finally but it was warmer outside (40 degrees). Could taking out the mufflers cause not enough back pressure on the motor and all the hot air not going through the cat to warm it up? I need to get the car running before winter sets in. Thanks, sweet8.

 

No. Backpressure has nothing to do with your thing. That's just an abused term.
Check the usual suspects for failed starts.

 

https://www.rx8club.com/series-i-trouble-shooting-95/starting-issues-start-here-222584/

that'll narrow down your search

 

Update: I called Mazda they told me my car is flooded, they gave me the free towing number and they will deflood my car for free and replace all plugs and could.