My car has had a surge problem since i built a new engine.

had it on a gas analyzer today ,and it surges because its so weak 0.45% at idle.. and thats max on the ecu fuel adjuster if i unplug the lambda sensor the co raises to over 6.00% because its obviously max rich ,but it does idle nice rich not hunting like it does when weak.
the fuel pressure is 3.5 bar pipe off.


so i get home and take the plugs out No 1 plug is wet and black with fuel but all the others are ok/weak white. the problem must be to do with the rich cylinder making the lambda weaken off ,and this in turn is making all other cylinders weak


what can make no 1 rich? i swapped plug and injector and its exactly the same