How would a faulty Cpu present itself?

I have made numerous thread on the issue of stuttering but I will copy some here if you are interested.

I stutter in some games, not all. Most notably PUBG and Fortnite, which stutter so much that it's unplayable. All of my hardware works fine (from what I can gather) and I've done an insane amount of troubleshooting,100+hours.

While logging using MSI afterburner, it is clearly my frame time which goes wild and sometimes goes up to the thousands, constantly spiking.

This is the list of things I have tried.

1. Checking temperatures and clocks of all of my hardware
2. Run stress tests and benchmarks (stuttering in Uni engine Valley and Heaven)
3. Installed games on an SSD
4. Reinstalled games multiple times on separate HDD
5. Ran Windows Ram check etc.
7. Flashed my motherboards BIOS to the latest version 9.
8. Tested separate PSU's (Evga 650w Gold g2 and also Evga bronze 550w)
9. Powershelled Xbox app from PC
10. Installed 6 different Nvidia drivers, some old and new
11. Various windows creator update modifications. Disabled control flow guard for specific applications.
12..Installed old version of windows 1607
13.Played with page file and affinity option while game is running.
14.Fully Reinstalled windows and formatted SSD drive
15..Installed games on separate hard drives working separately and together (as in windows on one game son another platform such as steam)
16. Changed SATA cables.
17. Bought brand new MOBO and installed (H81 chipset)
18. Removed and reseated all hardware.
19. Bought 16gb of DDr3 RAM.
20. Installed chip set drivers
21 (Update) Tried different internet connection, which I though might be the culprit)
22. (Update) Disabled HPET


None of this works. The only thing that slightly helped, as in, bought my frametime spikes to a lower level (still bad) , was disabling all of my audio drivers in device manager?

The only two things left tor replace are my Gpu and my cpu.Both show no problems temperature wise, not does it throttle or do any such stuttering while stress testing. My GPU doesnt go above 68C and my CPu hits about 60 in very intense situations.

Specs;

i5-4590 3.3Ghz
Gtx 970 Strix
16gb DDR3 1600Mhz
120gb SSD
2tb HDD
Gigabyte H81 Dv2 (rev 1.0)
Evga Gold G2 650w

Yeah, no problem, it's a cursed system it seems. i might try and do a £70 upgrade to an i7 4790 to see and it wouldn't set me back too much.