2001 Nissan QR25DD - P0172 Reappears After 5 Minutes of Idle: Diagnosis and Solutions

Hi, My 2001 Nissan QR25DD has a recurring issue with fault code P0170 (system too rich on bank 1) that appears specifically during idle after about 4 to 5 minutes of operation. The engine normally runs smoothly, with good acceleration and power, but once the idle reaches approximately 5:00–5:20 minutes, the RPM unexpectedly rises above 1000 (should be around 750 when warmed up), the Check Engine light activates, and P0172 is triggered. I've already tried several fixes: cleaned the MAF sensor, switched to 98 octane fuel, replaced the spark plugs with premium ones, and addressed a known issue where a metal rod in cylinder 1's spark plug was pushed upward due to oil leakage — this caused a ticking noise and minor knocking. After replacing that faulty spark plug and upgrading all plugs, the engine started reliably even when warm, and the misfire during cranking disappeared. However, the idle-related P0172 issue persists. I took it to the dealer who performed a TK (Twin-K) test, suggested faulty ignition coils or oxygen sensors, but after replacing all four ignition coils and both O2 sensors — with no improvement — they concluded the problem might be related to fuel injection. I've also cleaned the EGR valve, added injector cleaner, changed oil and filter. The issue remains consistent: after 4–5 minutes of idle, RPM spikes, P0172 appears, power drops dramatically, and I must shut off the engine, wait a few seconds, then restart to reset the system. I'm now considering replacing all four direct-injection fuel injectors — but that requires extensive access to the engine bay. Before doing so, I'd like to know if there are any other possible causes or known solutions for this specific behavior in the 2001 Nissan QR25DD with P0172 during idle. Has anyone else encountered a similar issue? Any insights into potential root causes — such as fuel pressure issues, exhaust leaks, or sensor calibration problems? Thank you in advance for your help!