Lenovo T490 Laptop Tuning issues

This Lenovo Laptop is a 4 core  i5 8650 with hyper threading disabled and most of the I/O.  I was able to get the latency down to 1.4ms  for the Servo Thread and 2.5ms for the Base Thread, by manually tweaking the Grub default command line and adding a service to start at runtime to control the fans and power level.    But with this result.  Is the latency withing bounds of running a Mesa 7i96S without issue.  I have disabled all of the I/O except for  the USB  and disk drive.   I had to change the SSD from a NVME M.2  to an SATA III, m.w , Because interrupts were showing up for nvme0q4 causing issues.   Evidenlty all cpu's have these interrupt queues by default and nothing can be done to reassign them. 

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash consoleblank=0 fbcon=blank:0  nvme.io_queues=2 isolcpus=managed_irq,domain,3 nohz=on nohz_full=3 rcu_nocbs=3 processor.max_cstate=1 pcie_aspm=off rqaffinity=0,1,2 kthread_cpus=0,1,2  ipv6.disable=1 i915.enable_dc=0 i915.enable_fbc=0 i915.enable_psr=0 i915.enable_rc6=0 intel_idle.max_cstate=1 intel_pstate=disable skew_tick=1 mitigations=off nosmt nosoftlockup nowatchdog  nvme_core.default_ps_max_latency_us=0 usbcore.autosuspend=-1"
GRUB_CMDLINE_LINUX=""

I did not run rt_setup.sh  -  because I see no history in the header about the package and its uipdate.   I do not know the vintage of the file. 

I think you mean usec not ms. Can you share a screen dump of
latency-histogram --nobase --sbins 1000 --show

Also we need to know the NIC you are using
realtek needs the dkms driver, Intel needs coalescing disabling per man hm2_eth

I suspect its probably OK. IRQ affinity probably needs to be set on startup as it does not persist.