You don't even know what you are talking about, if you don't understand what I posted earlier...
Just about EVERYTHING in an engine has to work together
Let me hold your hand and walk you through this.
(FYI all pics taken off of ebay listing)
NUMBER 4 cylinder ALWAYS runs LEAN.
Reasons:
Intake manifold - Look at it. Even though the plenum is tiny, they managed to have the air path have almost a straight shot to the number 4 cylinder. Yet made it so the air has to basically do a 180 to reach the number 1 cylinder.
Fuel rail - Returnless fueling system (no return line). Where does the fuel enter the fuel rail? From the center. Given the point above It would make more sense to have the inlet of the fuel rail, enter from the rear of the rail, as it sees the most pressure. This would mean, more fuel to the cylinder getting the most air.
Exhaust manifold
Now lets take a look at the exhaust manifold.
You see where the collector is? (not going to explain what a collector is, in terms of exhaust)
Unequal length runners, means uneven exhaust pulses, meaning loss of potential power.
The runners aren't even directed towards the collector.
Now with everything I said about the intake side, look at the exhaust manifold.
The rear cylinders are more free flowing than the front cylinders.
If the turbo and collector were moved forward, it would cause a slight bit more back pressure for the rear cylinders, negating some issues of the rear cylinders running lean.
THIS is why no one reputable makes a "log" type manifold.
The reason why some manifolds crack is because a combination of the following:
Sh!tty welding (a large number of issues with this. not going into)
Stress because of weight (a turbo hanging off of it without added support)
Incorrect material used (alloy type and/or thickness)
incorrect tempering/cooling (applies to both welded or cast manifolds)
Welding onto cast iron AKA welding a normal manifold into a turbo manifold. (different alloys welded together don't like to stay together for long, especially when heat cycles are involved)