Hi yes, I'have found a solution. Problem is that stock cooler can't handle so much heat. The solution is for Optiplex 7090 Tower, case SFF is to small. You need to replace stock cooler with cooler: Silentiumpc - "Spartan 4 MAX" it fit to Tower case and when You mounting it you need to skip mounting under motherboard parts. Under motherboard stock base fit to Spartan 4 MAX.  After new CPU cooler mounted, temperature will drop down to max 75 Celsius degrees. After replacing original CPU Cooler and FAN You will have alarm on CPU diagnostic test. Problem is with low RPM of Spartan 4 MAX FAN but it works. If You  really want to pass all diagnostic tests You need to replace Spartan 4 MAX FAN with higher RPM FAN : Corsair "ML120 PRO" it needs to be PRO because others have to low RPMs. This configuration works for me. But after that upgrade You will see that CPU Temperature throttling is no longer an issue. But new issue will appear, CPU Power throttling. In my case Intel i9-11900 looks like for some reason CPU start to throttling when CPU power exceeds 90W. Then cores frequency drops down to 3,2GHz. I fix it partly only by using ThrottleStop software. Now when all CPU cores are on heavy duty frequency drop down to 3,7GHz and temp is about 65 Celsius. Good luck
I'm currently have Optiplex 7090 MT with Intel i9-11900, I also replace stock Fan with professional cooler Spartan 4 MAX with big FAN. The problem is that Optiplex can't handle this FAN. On diagnostic test I have information that "CPU Fan Failed to respond correctly". Error code 2000-0511.  The Fan is working but Optiplex not control its speed on OS Windows level, just simply work on low level of rpm like 400. It's not possible to control RPMs on Windows level. So on Windows I have situation that it's throttling because Optiplex not increase Fans speed and its always ~200-400RPMs. What is the cause : When I'm doing Advanced CPU FAN Test, Optiplex is trying to force FAN to speed-up to Target FAN RPM up to 4000. RPMs on Spartan is growing as it should but stops at 1600 RPM because this Fan can only have 1600 RPMs. So it's looks like Everything is working fine Optiplex is controling RPMs on that Spartan 4 MAX on BIOS level, but somewhere in BIOS we need to set max CPU Fan RPM to 1600. It was possible in previous version of Dell Desktops BIOS but in this version it's hided. It is looks like Optiplex 7090 works only with Intel stock CPU FAN and it is not possible replace it with better quality FAN. None of known software can control CPU Fan on Windows level. To speed it up. What is the solution for that?
Optiplex 7090 MT how to set correct maximum CPU FAN speed in BIOS