Next I researched and bought a $100 ebay header for the Sentra. The Engine light came on after about 50 miles of driving and stayed on due to the pre-cats being eliminated and the main cat apparently not being able to do the trick for the O2 sensor.
It added an annoying drone and rasp to the otherwise already raspy stock exhaust. Otherwise I couldn't really tell if it was any faster, except that I stepped on it more than usual.
Afterward I got a Flow Master 40 exhaust, having viewed a youtube video of another Sentra that used it and sounded very deep and no rasp. Of course it was an older '95-99 1.6L Sentra and now I know why that owner sold his car.
The Flowmaster further destroyed the peace inside the car if god forbid I needed to accelerate at a decent pace and drove on the highway more than 45-50 mph. My usual driving is done at 60-70 mph with the engine RPM at around 2300-2500. A few months later I learned a resonator could help with rasp and droning. Got a 14" put on. It only worked for few short months before the drone seemed to have come back.
Next I bought an 18" resonator to try and fix the problem. That seemed to have worked better, only slightly. At least now around 60 mph it was a tad less annoying.
Sick of the drone after 7-8 months, I researched some more and found that a straight-through Magnaflow oval muffler would work wonders to reduce the drone and rasp inherent to the FlowMaster 40 mufflers.
Had this setup for approximately 8-10 months until it came time for inspection. I removed the header and had the original exhaust manifold put back in, realizing that the $600 I had spent on the car at that point had probably not done much to decrease the 0-60 time of 9 seconds on my A/T 1.8L 128 HP car.
Now with no annoying rasp and just the deep exhaust of the resonator + Magnaflow exhaust, plus the grunt of the intake, my Sentra is now living out its middle years at 76K miles with synthetic oil and careful, gentler gas pedal usage.
My 2 youtube videos posted of the car in various stages with its exhaust, of course, gained some nasty and entertaining comments. It surprises me how much stupidity some people have and feel that they need to insult someone for trying to do something different, even if in the end the car is still slow or not.
What I gained from my experience with the Sentra, I took to my '09 Altima Coupe 3.5 and enjoy it as my daily driver with a super cheap sub $200 ebay exhaust and a Racignline Y-pipe. Those are all the mods my coupe is probably going to get and I don't know whether it's any significant amount faster or slower than stock, but the car's sound is pleasing to me and that's all it takes to enjoy it.
Moral of the story - The internet is a cesspool full of stupid people, and experiment if you want with mods, but stick to saving gas with a non-sporty econobox and save the mods for an actual faster car that will actually benefit from them in some way.
