no vacuum leaks, I recall Brendan having trouble with the O2 sensor before giving it to me. the montero runs for about 2 seconds before the CHECK ENGINE light turns on. and it really starts running rough. I checked timing 20 times now and everything lines up. How do I go about checking to see if its still working properly?

Richard E
1989 Montero - Stock-ish
1989 V6 Auto Raider - 5.3 Vortech Swap.
1987 Mitsubishi Starion 2.6t, soon to be 3.5
1983 Honda XL600R