i also own a hyundai accent executive 2008, which i got 2nd hand this May driven it abt 5k km at abt 19k(genuine) reading now.
other cars i have driven are maruti 800/alto, accent viva, HondaCity oldest. Some of these cars are not as powerful, still with accent i also feel the same problem mentioned here
i did injector cleaning, decarbonising, oil ,airfilter,filter,sparkplug,gear oil, clutch oil, break oil change at 15k. Got the car checked a couple of times at two authorized service centers, couple of local service centers and all of them find my car to be in good condition with no probs.
I think another problem with this cars is with Load, even the load of a full petrol tank reduces it performance, and i noticed if you fill during night(petrol relatively cold) it feels slightly better. Also tried some petrol tank additives, yet to try premium petrol.
Tried Reseting the ecu(adaptive data, by removing battery terminals) couple of times and driven revving high, but that doesnt make much improvement for the long term.
lately i had been considering going ECU remap route, but unsure..Anybody with accent petrol ECU remap experience??
Also how about iridium sparks plugs and cables, may be they can smooth out the uncertain 2nd to 1st gear change region??
@muni_phantom: hows ur experience with AirFilter update??