I bought a full set of front and rear Dobinsons coils for my '02 4runner sport edition and installed them with new 5100's (front and rear) and two months (TWO MONTHS of all highway driving, no offroading at all) into them they have already started to sag on the front drivers side. I've had...
Like most other, don't go with the cheap aftermarket replacements. Spend the money and get OEM. I tried the aftermarket and it ended up with my 4runner broke down for a week while my OEM injectors were being shipped.
I had similar issues with my 2002 3rd gen. Some of my coil connections had worn out and had wiggled loose. after replacing the ignition coils, wiring and plugs I haven't had any issues.
I had the same thing happen on my 3rd gen 2002. when I opened up and checked the wires, almost all of them were worn through. once I replaced the broken segments everything worked just fine.
I had the same issue with my 2002 4runner. when I took the wiring harness completely out I found that the wires were worn out farther in. they had stiffened up and a few of the wires actually broken and were shorting out.