How can I stop i7-9700 from throttling ?

Hi, I have an ASROCK Deskmini 310w with an i7-9700 with a Noctua NH-L9i, 32 GB RAM and 3.5 TB total storage. It has a base clock of 3.0 GHz and boost clock of 4.7 GHz. I can't seem to stop throttling with scaling_governor set to performance, min_scaling_freq set to 4700 MHz and cpu temperature throttling disabled in bios. Tried increasing power limits also. Everything I have tried leaves me with 3.2GHz to 4.6GHz with temps of 59C to 71C. At around 70 it kicks down to 3.2 and ramps back up to 4.6 when temp drops below 60C. On longer runs it gets slower and slower falling to 3.6GHz max and even did that when I had temps at 63C max. I had made a shroud to isolate intake from exhaust that cut temps suprizingly well, its just a pain in the ass to get it in there. I have a larger cpu cooler fan arriving tomorrow so shouldn't need shroud and temps will be back around 60 or hopefully a lot less. But even in low 60's it throttles down to near base speed. I am at a loss on what to do to get an average above what seems to be around 3.5GHz on just a 10 minute run. Can someone tell me what is going on or how to fix it ? I could really use the help. Thanks