Thank you for your reply!
So since last I purchased a new MAP sensor and installed, as well as new seals for the EGR with added high heat sealant.
I cleared adaptations and fuel priming afterward. This got me the longest run with no code- 55 miles. Then they popped up again.
It seems that running it on the highway the Short term fuel trims stay within -1% up to 5-6%. The issue appears to be when stopped, at a light or something, and the truck is idling.
I think I am going to take it to the dealership, I cannot get the registration without emissions- I have been driving unregistered for 8 weeks now.
It really is bonkers how this works!
Thanks,
James

 

How is the idle? Is it steady at 600-700 rpm, or does it fluctuate and stumble?

At this point I’d lean toward MAF sensor being an issue. What did you replace it with? You’ll want OEM or Denso. Bad MAF or dirty throttle body are common issues for poor idle, not sure if they will trigger a lean code, though.

 

So it is pretty consistent at 695 RPM, give or take. At times, there is a slight deviation, but it does not stall really. As for MAF, I replaced with Denso.
I may, put the fix seal or lithium grease on the Throttlebody seal and see if that helps.
But overall, the fuel economy or overall performance has not been terribly affected. On the highway with 32.5" KO2s at about 14mpg. Maybe a little less than before the codes showed up, but nothing significant.

 

Hard to say with this info, but those symptoms could still be one or more bad injectors, as has been suggested.

 

Thanks,
I think it maybe a bad injector gasket- I had a couple of other anecdotes suggesting that.
I will investigate that aspect and keep all updated.

 

Updates?

 

When I first bought my Rover from the previous owner, I had these exact same codes. It's been a while now, but LTFT were around 15-20% IIRC. The MAF was new as they told me. As I was hunting around to replace parts, I ended up replacing the o-rings on the PCV, PCV crossover o-rings, I permatex'ed the EGR, sprayed starting fluid around the intake box to hunt for plastic cracks and replaced the seals for the (cam timing sensors?) in the valve cover, ran injector cleaner. This lowered the LTFT to like 12%, but the culprit all along was running an aftermarket MAF. The thermal wire is not the same between aftermarkets and the OEM Denso. After installing the OEM denso, LTFT 1-2%.