bro, good to hear that. U are lucky to have the opportunity to test on dyno n on road..
hehe.. fyi i oledi installed the marco 421 cheap one to my raralution 1.8mt since early this year. i dont know whether it is 2.0 or 2.5 inch pipes.

i think some of us did installed this 421 oso. however, some of us may not like the water flow sound.. but im reporting that the sound has reduced somehow.. maybe got carbon build up in the xtractor n reduces the noise. or i got used to it. 

personally for normal urban driving, overtaking n accelerating, (not like our jack the felali killer dring style ) the 421 i used give balance and overall torque improvement across the rev. of course i don't expect high bhp but if got then its a bonus! never yet tested on dyno but butt dyno feels fantastic.

smooth fast pickup straight from 2.5k to 7k or over redline (haha thanks k3 for the revcut removal n copy remap) . that one u can ask botack, eiraku n alonso to verify..hehe but 421 extractor alone could not perform well without other mods (copycat remap, groundings, vs zaptor, air hole mods, raliart snorkel etc.. handling n suspension plays important role also on how your vehicle behave during hard accelerating). with grounding n zaptor vs the humming much reduced n your car will response much better..

i use the 421 marco coz the design more or less almost same as the supersakit minus the stainless steel finish and i wanna maintain the ori cat back. i think the 421 extractor is good enuf mod as the ori piping from the extractor straight to the rear muffler is oledi quite big.

thats my humble review n opinion.