I put a 2.0 GA code motor in my 72 and 1cylinder has a 20% leak down however the compresion is good in all 4 over 100.
I can not seem to dail the motor into perfection. Is the leak down in that cylinder causing this?The motor starts right up idels good and does have power just sometimes it studders at high rpm and speed.When the motor wakes up its fast as hell.The FI system is all new however the harness is old and cracked with some bare wires showing.I am getting a reconditioned harness tommorrow in hopes that will solve me problem.
Any thoughts?

unlikely leakdown is causing your "studder" but it could be a concern with regard to it's source. recommend you track it down to either rings/cylinders (less serious) or valves/heads which are more of a concern considering possible damage due to valve or seat failure. you should be able to audibly(?) locate the leak. may need nothing more than an adjustment or retorque.

I do realize a future top end job wil be needed,my real question is about the FI.are these things so touchy that a leak down would cause me to never be able to get the fuel system right?
The studdering problem has gone away a few times and the thing runs good.I understand faulty wireing is to blame for most FI problems.
Also if the ECU is not right would the car just run bad or not run at all.
My thoughts are to go after the wireing and stuff on the out side befor pulling the engine again tearing it down.