Prelude 4th losing power, noisy

Hey guys,

I've got a '96 4th gen prelude.
125,000kms

After about 20mins driving or 15mins in peak hour, as the temperature gauge reaches half way, it starts losing power.

The engine becomes noisy/rough. The temperature gauge never goes past halfway though.

Although it's annoying, it doesn't bother me TOO much but could this be a sign that some bigger problem might happen in the future?

After this symptom started occurring I have:
Flushed the coolant
Changed engine oil (Honda FEO)
Changed spark plugs + leads (Bosch)

Still not solved.

I've also posted this in preludeaustralia.com but I think more people use this forum.

Cheers

engine seems to be cooking. hows your water pump? is it pushing water properly. whats the condition of the head gasket might not be a bad thing to check for leaks there.

I'm not sure if the water pump is pushing the water properly, how can I find out? Coolant doesnt seem to be mixing with engine oil, is there another way I can check for leaks in the head gasket?

are you losing water? before you take it for a drive, check the water in your radiator if your losing water that means there is a leak some where. if your engine oil is fine your head gasket is fine.

Is it a VTIR? Are you using 91 or 95 RON petrol?