Lean on Both Banks

My 99 Rodeo's IMG's were leaking so badly back in the winter that I could hear the sucking sound from the driver's seat with the windows rolled up. At idle, it would run very badly and would even die at idle in Park. And I would get CEL codes 171 and/or 174 - no surprise there.

I replaced the gaskets (which was quite a job, IMO). The old ones came out in pieces. Now the truck runs fine. But...

I'm still getting codes 171 and 174. Usually just one or the other, sometimes both. They only happen at idle or low speed. Once the CEL comes on, I can reset it with the Harbor Freight reader and drive for 300-400 miles at highway speeds without it coming on again. Then, when I get to where I'm going, it may or may not come on again - at idle.

It would seem that if I were really running lean, the situation would manifest itself at all speeds, not just at idle.

I'm thinking maybe my injectors are somewhat dirty. The truck has nearly 140K on it and and I've never cleaned them. I've also read it could be the Mass Air Flow sensor but I took that apart it certainly looks clean.

Anybody ever had this problem after changing the IMG's? Any helpful thoughts?

Thanks!