Faucet still leak after replacing the stem assembly? I'm having a difficult time correcting my leaking faucet, I've tried almost...

I'm having a difficult time correcting my leaking faucet, I've tried almost everything but nil seems to work! I've had a leaky compression faucet for some time; at first, I thought it be all due to the old/worn out stem assembly. I was surely positive it be that damn old thing because when I took it out the faucet stopped leak. But now, after replacing that old stem assembly beside a new one, the leaking started put money on up again. Now I believe the problem may lie in the form valve under the sink...
I also tried looking up for pictures of my stem assembling, thinking I may be missing a section, but there isn't any.
Any suggestions or thoughts as to how to fix my sink is encouraged.
A investigational faucet doesn't cost all that much, considering all the time and aggravation you are going through, why don't you buy a hot faucet? does the faucet have a replaceable valve form??
There is a seat inside the faucet that the washer seals against to stop the river flow. If you rub your finger against it it should feel smooth. If there are nick, that is where the river is leaking thru. It takes a form wrench to remove a seat and seat wrenches are usually sold contained by a set of three because of the different seat sizes. The seats are made of brass, within are plastic ones but not replaceable (by me anyway) and should be available where you got the stem. yes progress to the hardware store and buy a seat tool. take out your elderly seats. go to the store, clash them up and reinstall them. or better yet. treat yourself to a new faucet
Answers:    other replace the faucet's seat when replacing the stem as a matched set.

the stem is worthless if the seat have a nick in it.

if you can replace the stem you are handy ample to replace the seat. it is located just below the stem. you will probably stipulation a special "SEAT WRENCH" to remove it and match it with a foreign one.

good luck. it's way cheaper than a investigational faucet.
Get a new faucet. that new assemble fits into a small form valve? not sure if that's what it's called. you should enjoy changed that seat when you had the assembly out. it's a cone shaped piece that have an X missing from the bottom (that's where the water comes into the assembly quantity before coming out the spigot.
take the assembly out again and look within the assembly hole that the valve came out of. you can but that piece for smaller quantity than $1.00. there is a tool that you place in that X hole that you later screw out. using that same tool you put a new one in. i've done that a couple of times. the hardware store that i purchased those pieces LENT ME the tool to do that duty. left a small deposit, and when i returned the tool i got my money final. it was an ace hardware store. ask the clerk at the store if they have a loaner policy. it is a form valve but not sure what you mean by beneath the sink.
good luck to ya