What you need is an engine tuner/builder. Probably easiest to locate a Renault engine tuner as the 440 uses renault-based engine.

This is an expensive and labour-intensive process though.

To get any significant power gains you would need to remove the cylinder head from the engine, have larger valves fitted, ports cleaned up and opened up further.

Then select a 'wilder' camshaft with bigger lift and longer duration.

Throw away the normal intake plenum and throttle body and fit 4 separate throttle bodies to the engine with correctly spaced intake 'trumpets'. (going to be very difficult on this engine though.. litte space.. so may need to limit the camshaft to a 'mild' type that will work on a plenum and single throttle body setup)

Add a new exhaust manifold (4-2-1 style) with tuned lenghth primary and secondary pipes for maximum torque gain.

If you want to increase the rpm limit on the engine then make sure your pistons, connecting rods and crankshaft are up to the job. You may need to change to forged pistons and connecting rods and perhaps a steel crank... Engine builder should know about that.

With new pistons you can also bump the compression ratio up a little to somewhere around the 10.5 to 11:1 mark.

Then ditch the normal ECU and install a programmable ECU and have it mapped on a rolling road.

My guess is that would potentially give you an engine capable of pushing 160 to 170 bhp. Depening on how good the head flows it may be even more. You will need to rev the balls off of it though to get all the power...

But.. It's gonna cost 'ya to build it and it will become more maintenance intensive and damage-prone.

Bye, Arno.