The only difference is the tacho needle moved a bit quicker from about 3k rpm so my torque was likely to have increased. You wont notice a good difference unless you have supporting mods such as a cold air intake and even cat back.
I dont think you'd notice a difference between 4-2-1 extractors and 4-1 unless you've done some serious engine modifications, besides 4-2-1 extractors give better low end torque which is what you need for the street, where as 4-1 are more suited if your constantly above 5k rpm
In terms of recommending them, i haven't tried out other extractors so i cant compare, but like i said, these look great, fit great, do their job, but their downside is the metallic rattle that comes between 2-2.5k rpm, but this sound doesn't happen when you floor it say from a stand still, only when your cruising at 2k rpm then decide to put your foot down whilst in a high gear, i hope this makes sense