I thought I would post this, since I know so many of us have this issue. I had the P0089 fuel code coming on and off for a long time. No driving issues, just the annoying code, which woud come on and off on a daily basis. As others, I tried replacing the fuel filter and pulled the hpfp and replaced the cam follower. I did not replace the pump, just the follower. After about 78,000 miles it was preventative maintenance and surprisingly it wasn't bad. Anyway, this did nothing to fix the P0089 code. I figured since the car drove fine, that I could live with the intermittent check engine light (more on than off). I just went about checking the codes every so often to make sure no new code(s) were thrown. Fast forward- I recently had the car in the shop at 84,000 miles to replace the coolant flange due to a loss of coolant coming from the back of the motor. I purchased the ECS kit which comes with a new temp sensor. Well, it has now been almost 800 miles and a few weeks (I took a 400 mile trip out of state) and no P0089 code. I don't know if it had something to do with the temp sensor, but that is the only electrical piece that was replaced. I will post an update in a few thousand miles if still no code, or if it comes back. I know people have tried everything and not been able to solve this code, and it makes no sense to me that a coolant sensor would fix the code, but I won't complain.