2017 MacBook Pro 13" WIFI slow (compared to other devices)

Hi,

I've noticed performance issues, drop outs and slow Internet on my MacBook Pro. Weirdly, other devices achieve around 70 down on the Internet speediest and my MacBook achieves around 10 - 30. I've tried clearing cache using an application called Disk Diag. It didn't make a difference and also tried the usual SMC reset etc.. I've even changed the WIFI location and DNS settings etc... didn't make a difference.

I've noticed it stops working when I plug in monitors etc.. or even the charger. I've done some research and it's to do with interference and the tinfoil solution kinda works. This issue happens even without anything connected and near the router.

I'd appreciate it if someone may know a fix.

Thank you.