Gurdas and I will have to meet up once he's all exhaust and mapped up and make a video of 2 Nur Spec R equipped STis!
That's because you have no turbo to act as a massive silencer
And sorry, but lol @ Nur Spec on a Yaris
Don't forget, as you have a wagon, it really makes it boomy.
Strangely enough, when my Dad had a silly loud exhaust on his WRX, he padded the boot with some like cotton wool fabric. Couldn't have added even 1kg of material, yet majorly reduced the cabin boom.
You did what what? Did you not buy a filter as well as oil? To change both at the same time?
I've always found it really easy to access If it's really tight just stab a screw driver through it and twist. Then replace with new!
Remember to prefill the oil filter before fitting. It takes a while to do as they really soak up quite a lot of oil.