Here's what you need: a shank brush (it's made for that purpose,)and bristle pipe cleaners, both regular and tapered. The tapered ones will be especially helpful. And now the kicker: dip the aforementioned in grain alcohol, available in many states at most liquor stores. it's sold under the brand name Everclear, among others. it's 190 proof and it really does the job in cleaning out the gunk. Just keep running your bristled pipe cleaners (or shank brush) dipped in grain alcohol and scrub away, until they come out clean.
If your state doesn't sell grain alcohol, buy the highest proof vodka you can find.
When you finish, you can run a cleaner dipped in bourbon or Irish whiskey, to leave a nice taste behind, although I've found that the grain alcohol works just fine for that purpose.
then, to keep the problem from recurring, clean your pipes each and every time you smoke them. It really doesn't take long for a pipe to get fouled up, and keeping them clean as you go will go a long way toward ensuring the kind of smoke you want to get.
I know--I've been doing it for over 50 years, and some of my pipes have been with me that long and taste just as good--and better--than when I got them.