Car: 1998 Lexus ES 300
160,000 miles
California emissions (an answer to a question I've been asked by parts dealers)

Codes: Igniter

History and symptoms:
At one time, the keys were lost, so, instead of dealing with Lexus and paying for a new key, the previous owner had a friend swap the steering column with a Toyota Camry. The car ran with no big issues for around two years. The problem began when the rpms would dip and sometimes die when I would stop at red lights. I could start the car back up and get home, and as long as I slightly revved the accelerator when stopped, it would not die.
The car was taken to a shop and they replaced the igniter. It ran for about a month before the same issues began again. I then took the car to a Lexus place where they changed the timing belt for a hefty price. The car ran for another month or so before doing the same thing.
The issue has gotten worse. It has began cutting off just after it starts. It will start every time, but cut off after. If I disconnect the battery and come back the next day then reconnect, it will start and idle for about two minutes before cutting off. After that, for the remainder of the time I'm checking on it, it will cut off just after ignition.
The codes still show igniter, but a recent replacement with a brand new one made no difference. We checked that the fuel pump was running and it is. We've checked the coils and spark plugs also. They are good. Also, there is a drain on the battery. If a battery sits for a few days connected, it will drain down. Battery is new. The gas is clean. My brother in law wants to try an new computer, but it is a significant cost. Its not a part I can go buy then return if it doesn't make a difference as they have to program it for my particular car. I don't know how to do it myself. I want to be sure its not a simpler issue like a sensor, a fuse, or bad wiring before i invest in the computer.

This car has been a problem for over five years now. Where would you suggest I start on this one? Does this sound like anything you've repaired in the past?

I know this was a long one. Thanks in advance. Big fan! Thanks for all your content!