Any cel?
You'll need someone with a scan tool to read data in order to narrow down the issue.
Could be a clogged cat converter issue as well.
However, please visit a knowledgeable mechanic in your area in order to actually diag the issue.
You can get many suggestions and tips here, but it's difficult to know until the car is actually diagnosed.
Make sure any intake piping is also sealing properly and there are no tears or holes in your intake pipe.