Engine sound changes when car gets warm? Tb48 - read details inside

So as of late, after about 20 minutes of driving and the car gets warm, the tone of the engine changes completely, the toughness goes away and it sounds more like a 8 ton truck or something whining , exhaust sound changes completely and you can notice a power loss, unable to get a video right now as its in the shop getting diff gears swapped, but it goes from sounding like a tb48 to sounding like a bodgy Mitsubishi magna lol.

I've got a new intake pipe coming I'll fit as soon as it lands as I think it may have a crack or a hole due to the age + clean the throttle body while im at it, I'm cleaning the mad sensor on a maybe 2 week basis and it seems to help but not fully. Any ideas where to go from here on boys? Starting to do my head in..

Some updated info about car -


260,000 ks ( just had an engine reco as it was on gas + fit new billet oil pump gears - this done less than 1,000ks - 2 months )
Straight petrol
Pacemaker extractors + 2.5 custom mandrel bend exhaust
4 inch snorkel + airbox



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Sounds as if the inlet manifold is warping when hot or something similar. Is the ignition coil getting too hot?

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Originally Posted by mudnut

Sounds as if the inlet manifold is warping when hot or something similar. Is the ignition coil getting too hot?

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I'll check the intake manifold when I get the car back, spraying some wd40 onto the intake should do the trick right? If the revs increase I can be sure its the intake leaking? Surprised if it is with the engine being reconditioned 2 months ago, but you never know I guess

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Sounds like an exhaust issue to me aswell. When the exhaust gets hot the metal is expanding and maybe letting some cool air in, or hot gas out.