Years ago I bought a 'Mugen' chip off Ebay for my D16A6. My seat-o-the-pants meter felt like an increase in power. Eliminated the rev limiter so I was happy. Later when I learned more about tuning, I actually tuned my car on a dyno using some Moates equipment & Turboedit. Turns out the 'Mugen' chip was actually the stock maps from a PR4 ECU. When I compared the stock ECU with the 'Mugen' chip on the dyno, the two mappings made virtually the same hp and torque curve ....... all that really changed was the PR4 map was pig rich (10:1 afr) . No wonder my fuel mileage at the track was so crappy with the 'Mugen' chip. Where I used to run 1 1/2 hrs on a full tank (stock ECU), I was only managing 45 minutes on the 'Mugen'.
Anyways, I used the PR4 maps as the basis for tuning and adjusted the fuel and ignition timing. Managed to increase the hp about 11% over stock but more significantly, increase the torque's peak and duration by about 14%, with 90% of the peak torque available from 3100 to 6500 rpm. Also held the afr to about 13.5:1 across the rpm band. Now I get better power and fuel mileage than the 'Mugen' chip, but it took 8-9 dyno runs and a little bit of reading & an electrical engineering buddy's assistance to accommplish.
My point is that the chip may feel different but you really have to dyno it to have credible comparative results and if you can find some one with a chip burner [ or buy one from Moates.com for about $100 ], you can find out whats really going on inside it, rather than taking someone else's word or guessing. Not all sellers are asshats but some unknowingly spout statements without truly understanding what they are saying.