Iam only working every second week. Spent a few days servicing all the bikes ready for the season. I dont work on bikes much these days, and forgot how much I enjoy it.
BF XR6? We have used this, its not to loud. You will be happy with the sound. It has twin tips.
https://www.ebay.com.au/itm/2-5-CAT-BACK-SPORTS-EXHAUST-BA-BF-FALCON-6CYL-XR6-NON-TURBO-SEDAN-DUAL-OUTLET/360642268637?epid=1042725663&hash=item53f7f44ddd:g:HQkAAOSwhcJWQUZi
Yeh, I know a guy that runs over 450, BUT he tunes his own car. Its all in the tune to make the rods lasts. And E85. Also having a larger turbo to run less boost at same power helps.
I have done it many times without compressors, just use rattle gun. It is very dangerous. The new springs being lower will go on easier.
If you are smart you can use the cars weight and jacks to do it in the car.