I try to tell you lads on this website that if you are thinking about tunning up your standard k10ma10/12.the 1st thing you should change is inlet manifold and carb,thats even before exhaust manifold,,you got to get more in before you can get any more out...
you spend about £400 on a 4 into 1 exhaust manifold and system it looks and sounds better but you'll only see 3/5 bhp tops with the standard carb/inlet its a waste of money
open up the inlet tracks and a better carb you'll see 15/20 bhp easy and thats with the standard exhaust setup
Take my racecar for instance the engine is standard just really blue printed,standard cam with only say 40thou off the head,bottem end standard just balanced.no lightening aloud
Just by fitting a different inlet manifold and better carb i get around 25bhp extra@flywheel..
Changing the exhaust system after the inlet/carb then you'll get better result