Removing the catalytic converter:

It is a potential fail on your next emissions test. Modern catalytic converters offer very low exhaust restrictions so removing it gives very little added benefits. Its also very expensive to replace so I hope you kept it and didn't leave it at the mufflershop. The only potential restriction would be if you were going to install force induction on your 1.4L engine.


Exhaust systems work on your 1.4L car...

If you are looking into racing your car, you are potentially wasting your money because you cannot even match the power output from a stock 1.6L engine with what rational mods you can do on your 1.4L motor. And your mods will increase your fuel consumption. 1.6l engines could use 2 inch pipes if has enough mods to make it worthwhile. 1.4L engines would be better with smaller like 1.75inch to retain low end engine power.

The trick is not bigger pipes is better, it is keeping the exhaust gasses velocity relatively high without increasing exhaust backpressure much.

As for the "sound", you might think it's macho but its just noise to anyone else around you. You can get the same "performance" if you had a pass-through full size muffler installed and it would be quiet at low to mid range RPMs as well. The droning sound under your car would literally be a headache and potential cause of hearing loss on longer drives.


Header design...

Typically 4-2-1 is a more practical layout which retains better torque in the mid range for engines with torque that peaks in the middle of the rpm range like more common nissan and toyota engines. For honda or mitsu engines, 4-1 is a better design because hp & torque peaks at near the redline.


But overall...

If you really want to race your car, you might want to save your money for real mods and you can start with getting a bigger displacement engine, like a 2.0L n/a engine or better. But frankly, there is more to having a fast car than just more horsepower under the hood.