So you're likely looking at something like the following:
- Headers & Y pipe
- Replacement cat
- Replacement muffler
View attachment 36139View attachment 36140View attachment 36141
These are Larini's offerings for the Evora but the Emira will be extremely similar.
Passing emissions test is dependent on what your local jurisdiction does and how thorough they are.
The majority of the emissions tests comes any combination of three tests:
Visual Inspection
Here they visually inspect what is easily visible from on top or under the car to see if anything has been modified that warrants further investigation. You would
likely fail a visual inspection since the headers are easy to see with the plastic engine cover off the car.
Tailpipe Sniff Test
Here they will insert a probe into your tailpipe and measure pollutants and pass / fail based on a threshold level of pollutants while driving on a dynometer and a prescribed speed. You would
likely pass as most of these tests are fairly lenient and meant to test older cars.
OBD2 Readiness Monitors
Here your ECU monitors oxygen values from the upstream and downstream sensors before and after the catalytic converter. As long as you're using headers and a catalytic converter that has ports to plug in your oxygen sensors and the extension cables that come with the exhaust like in the Larini above you should be able to pass the readiness monitors for your ECU.
Your locality matters a lot, here in California we usually get OBD2 readiness monitor and sometimes a visual inspection if the emissions tech is being thorough. MOT in the UK is more about visual inspection and tailpipe emissions sniff test -- but I believe you're exempt from the emissions testing for a few years.