I took out my new to me pistol. (A Springfield P9 made by Tanfoglio) It mostly feed alright with WWB however I had multiple stovepipes with it.
I was curious what suggestions you'd all have to reduce/eliminate this problem? Lighter spring? If so how light? Would the comp have an effect on the reliability?

Thanks in advance.

if the comp isn't supported by a guide rod, the additional weight can cause unlocking problems...make sure the ejector is not rubbing the slide... try a heavier bullet weight... lock the slide back and let the spring take a little set for a couple of days... then try lighter springs, possibly main in addition to recoil

When ever a gun has an issue first two steps are different ammo and mags. Try a full power ammo like Winchester NATO ball. Most ammo out there today is the least power possible and still be within spec. Most of the time if you up the pressure velocity or bullet weight out of the basement ( where all bargain ammo resides) any functional problems tend to go away. Yes you do get what you pay for - minimal ammo cost= minimal results(accuracy reliability  etc)

Thanks for the advice. Also wanted to add that the cases didn't eject far at all. Maybe 3 feet away at most with many falling at my feet.

This is something one of my pistols does also, so I would be interested in an answer to this as well.  I thought it would be and extractor problem, but that checked out okay.

Usually the first steps are to try different FACTORY ammo that's high quality, and to check the extractor for proper shaping and power.
If there's a problem with the extractor the cases can slide out of it before the ejector gets a good bite.

Next is to check the ejector for breaks, chips, alteration, or malformation.

In the case of a gun only ejecting a few feet or the cases more or less just falling out of the ejection port, you'd look at too strong a recoil spring, or the presence of some sort of recoil buffer.
Also comps may add too much weight and slow the slide speed down, or I guess a super effective comp might reduce slide speed too much.

If it's possible, remove the comp and see if that has any effect.

You can buy different power recoil springs direct from Wolff Gun Springs.  Carefully experiment with lighter springs, starting with a factory spec spring and working down one weight at a time.
Watch for things like frame or slide battering and don't go too light.

Yeah, that one sounds oversprung to me.

Absolutely. WWB ammo, in my experience has smaller rim dimensions than other manufacturers... Others here and that other website I better not mention report the same. Next I look at a weakened magazine spring... Finally I look at the extractor and extractor spring as a possible culprit.

I would completely take down the slide and clean, inspect and lube. Polish the chamber with Flitz a cotton swab wrapped around a brass brush on a rod and a drill.