Modification - 4-2-1 Extractor

Out-manifold

Catalytic converter and out-manifold

2 piece 4.2.1 extractor

As you can see, hardly any space

Oxygen senor placed a distance away from the engine to prevent idiot light blinking

Yes, eventually, the out-manifold got changed in favour of a 4-2-1 extractor, to my knowledge, the first of it's kind in Malaysia. The custom set consists of a 2 piece package primarily because the Peugeot 407 engine bay is very narrow and it is more practical for the set to be made in 2 pieces. A new stainless steel flexi-hose was fitted between extractor and mid muffler.

How does it performed? Firstly, there is more exhaust efficiency but which the material of the stock mid and rear muffler could not handle from 1,500rpm onwards and resonance harshly to the extent the mid muffler had to be replaced with tougher stainless steel version of the same dimension. Secondly,  resonance shifted to the rear muffler so that too had to be replaced with tougher stainless steel version of the same dimension. Only then did resonance end. The tougher stainless steel muffler gives a quiet but deeper exhaust note then really roars like a lion when I floor the accelerator pedal as the extractor delivers optimum exhaust efficiency. 

I would say the 4-2-1 extractor delivers more than adequate performance for my needs. It is now silky smooth throughout the power band making driving such a joy to feel even in slow cruise.

Do I ever intend to sell the car? Not if I can help it.