Cleaning Carbon Build Up in Pipe, How?

[395Rider]

I am putting a Paul Turner Pipe that my bro let me borrow on my 86 TRX250R to find see the if I can harness the low and mid range power in my bike. Before I install the pipe, I would like to clean out the Carbon build up. What is the best solution to dump it into to get all the crap out of it?

I imagine I can get better performance out of the pipe if I get all the crap out of it and it will eliminate a variable.

Please let me know the best cleaning product that will get the job done. I am willing to leave it sitting for a few hours in some type of cleaning solution.

Thanks!