My 91 300zx passed the smog inspection but failed the visual because the timing was off now what can i do ?

Visual test fail is visual white smoke out of the tail pipe?
The engine seems to be burning something it shouldn't, such as coolant, brake fluid, oil. It may have a check engine light on or may not. Give it a leak down test and check for blown gaskets. Look it up in youtube or google it.

The smog check requires a visual inspection of your check engine light. It has to come on for a bulb check at startup to make sure it's working. But, the light must go out after starting the engine(it cannot stay on after the engine starts during a smog check). If the check engine light fails either of these two tests, the vehicle will fail the smog check inspection.
You need to have the cause of your inoperative check engine light diagnosed and repaired.

Take it to a different place to get it inspected, if there are no codes it should pass this test

Maybe not your answer, but it is related: Before going to have your car smogged, check your gas cap. Check the condition of the gasket, or o-ring, inside the gas cap. If is already drying out, full of cracks, get a new one. It will not pass the visual inspection. The smog technician, salesman, will try to sell you a new one for $15 when you could get it for $8 at your local auto-parts store. The technician will tell you that if you do not get it right there and then, he will have to fail your car on the visual test and you will have to comeback to have your car re-smogged again.
The cap might still be doing an OK job of sealing the tank, but it won't pass the Visual, especially if the tech wants to sell you a cap. You can tell if the cap is doing its job if you hear a hissing sound whenever you open the gas cap after running the engine fro a while. If it is not providing a good seal, then you might get a check engine light with a code about a failure in the evaporative system.
Just a little thing to check before you go and put yourself at the mercy of the smog tech.
For $15 you could get a locking gas cap, which might be a necessity now with gasoline prices being what they are, now.

I am only guessing but it seems to me an ECU that can't remember anything is probably faulty.

Inside the ECU or ECM, the brain, the computer can be divided into sections like the circuit board of a radio or a laptop. There will be voltage regulators, an obd interface, a memory for the fault codes and a memory for recent history and a memory for the learned settings. There will be a memory for the preprogrammed settings and drivers for the ignition and injection system and an active computer making sense of the sensor information in order to make constant adjustments.

Just as with most things built on a single circuit board they rarely fail en masse. Usually what happens is just one of the on-board systems fail even though the result for practical purposes is the same as if the whole thing frazzled.
Usually When an ECU fails it is one of the essential functions which leaves no doubt it must be replaced but it isn't inconceivable that any section could fail - even one or more of the memory sections...

It is probably the evap vent valve. A new vent solenoid valve has been redesigned to correct the problem you are having. I would recommend purchasing the dealer component.
I hope this helps.

remove the hose to the PCV and It simply pulls out and a new one is pushed in and hose is inserted back on. It's kind of like a cork. I can not believe they check for visual inspection. Here in SC, we don't have inspections. But anyways, GOOD LUCK

one end goes to intake manifold vacuum nipple and the other one goes to the evap [carbon] canister

if the light went out on it's own ,,,yes it should now pass inspection