Yes, it is allowed, as long it is within the limit of 25%. But it still comes back to the mounting problem. Anyway, I have did some basic modifications, currently the low end has improve a lot. The car start to have some "kick" from 2500rpm, but at around 2000-2300rpm, I feel there is still a dip in torque.
Mod done to improve the low end torque:
1) K&N Drop-in
2) Speedwork full exhaust system
3) Mythelogy lighten crank pulley
4) Denso Iridium IT20
5) Connectology Ground cables
6) Voltage stabiliser (Hot Inazma TYpe MR)
I will be doing a Dyno run at Speedworks this week, to see the effectiveness of the Hot Inazma. Too bad no dyno before all the mods above.
Cheers