I have been changing setup here and there due to some mod on engine.

Currently 1.5CC engine with 0.6 bar and abt 140 BHP.

I had tried remove Cat, then my low end speed is really like snail. Even stock 1.0CC car also can faster then me.

I put back the Cat and is fine, but from 120Km/h to 180 now is just abit faster then NA car.
Before put back the cat, is very very very fast climb up to 180 km/h

Now what should i do?

Change to Hi -flow Cat?
Change muffler with stock Cat...