Pipe Flavor Changing. Should I Ream?

That always happens to me when I smoke too fast. It makes the smoke unbearably bitter and reminds me to slow down the smoking. But from experience cake is always fine for me.

In addition to cleaning the stem, grab all of the ol' lady's cotton swabs, put a splash of vodka or everclear in a shot glass. Use swabs and pipe cleaners moistened with spirits to thoroughly clean the mortise and draft hole through the briar. Don't get alcohol on the exterior finish, as it can damage it. If the pipe is designed as a filter pipe, there will be a wider opening in the tenon end of the stem that needs swab cleaning, as well. Pipe cleaners alone will not clean the wider filter channel.

Cake level is a personal preference but letting a thick, loose cake build can trap unburned elements that may eventually cause impact to flavor. Most people who do keep a cake try to keep it between the thickness of a dime to that of a nickle.
Like many others, I scrub the chamber with a bent pipe cleaner or wadded napkin after each smoke to minimize buildup of cake and to ensure that what does build is a dense carbon layer.

I smoke a pipe for about 7 days at a time (3 to 4 bowls per day); I ream every time I change pipes using a Scotte reamer that is slightly smaller than the actual bowl size, thereby leaving about 1/16" of cake on it each time...I don't wash or wipe it though. I ream it out that frequently for exactly the same reason you are running into.

I don't think the flavor is changing because of the cake but from buildup of tars and other nasty stuff. I break the pipe down and use Everclear (or any other high alcohol content liquor for that matter, clear preferred). Dip the pipe cleaner in the Everclear and start running it through the stem until it comes out perfectly clean. Ream bowl to where the cake is about a dime thickness or a little less. Now use the pipe cleaners with Everclear and run them through the shank/tenon (or whatever it is called) all the way into the bowl. Repeat until the pipe cleaner comes out perfectly clean.
The other possibility is you smoked something with Lakeland Essence that ghosted the pipe. In that case, you may need to do the cotton ball soaked in Everclear routine in the bowl. That's not a bad thing to do anyway prior to reaming, it makes it easier to ream out the cake.

Give it a thorough clean first, but I’ve noted for my own preferences a good reaming can fix a pipe you know well but suddenly tastes different. It’s a go to fix.

A less intrusive way to eliminate unwanted flavours is to soak the bowl with damp coffee grounds and wait a few days. Obviously you still need to clean your pipe occasionally, but the coffee ground trick has always worked for me.