Carapils or Carafoam will work fine. A little wheat malt could be added and no one would be the wiser.
You could have a different problem, though. Diacetyl is a dependable head killer. Some lager yeasts are worse than others for producing diacetyl and you really need to take care with your D-rest schedule and preferably do a diacetyl test before dropping to lagering temps.
What was your fermentation temp and D-rest timing/gravity?

 

Define "true Pilsner" for me.... We're homebrewers, if you want to put wheat in your pils, put wheat in! I'd recommend using Carapils, you think the Reinheitsgebot crowd doesn't? Here's how a modern German pils is made: Grist about 95% Pilsner malt, but maybe a bit of Vienna for more malt flavor, about 5% of something to help the foam out because of that infamous 3-minute pour, lots of Hallertau. Bottom line, it's your beer - do what works for you! If you want a Bitburger or a Koenig Pils, do yourself a big favor and just go pick some up, in cans of course to keep it from being lightstruck. Otherwise (don't stop him, he's rolling....), if you want to try whatever in your Pilsner, try it....

That said, I don't think I'd go with wheat malt.

I think your problem is decoction with conventional modern malt. It's designed for single infusion or step mashes. I got some intentionally undermodified malt a while back and, with a double decoction, makes a great beer with a good foam stand but it's designed for decoction. In fact, the maltster states that it should not be used without a decoction mash. On the other hand, I read a quote from a German brewer a while back that decocting standard modern malts makes them just fall apart. Try adding the Carapils/Carafoam and a single decoction to develop flavor.

 

A truth: You want three opinions? Ask a brewer. You want nine? Ask two. A true pilsner is a beer that tastes like a pilsner. If I'm judging your pilsner and it hits all the pilsner criteria and you brewed it with sorghum? Guess what, you're going to receive a good score as a pilsner. There's a lot of dogma - beer lore - out there in the Webosphere. About the best advice I can give there is find reliable sources, then question them. Myself included.

 

The "true Pils" question aside...Yoiu need to judge whether the head retention is bad because of ingredients and mashing schedule or whether there's an issue with diacetyl and/or infection. Even a straight pilsner malt mash will give decent head retention. A classic lager will exhibit a decent head that thins but doesn't dissipate entirely so that there's always a light layer of foamy bubbling on the glass at the edge of the surface. Something as simple as adding a dextrine mash rest can help, as will Carapils, etc.
If there's a larger issue, the head will disappear completely and quickly without a trace of foam on top...as if you put a drop of oil in the glass. It's why soapy/grungy glasses can be a problem and diacetyl produces the same effect. It's a really common problem with homebrewed lagers.

 

I get great head and foam formation with all Pilsner ( and its variations ) malt. You don't need anything else, but you can try CaraPils. A head that doesn't stick and quickly dissipates is usually related to something else. Diacetyl can be one as mentioned above. In fact, many cheap/crappy tasting Lager-style beers ( at least those I can get a hold of ) have extremely poor head, foam formation and retention.

Foam and hed formation/retention are also aided by using malts with a slightly higher protein amount and hops. I never use less than 3.5 oz hops for 5-6 gallons, no matter of what style of beer I'm brewing.

You can read more here. http://beersmith.com/blog/2008/06/25/enhancing-beer-head-retention-for-home-brewers/

Not all beers are the same. Some beers will form head in the same glass others wont. Beer glasses should always be hand washed, with a light, gentle, detergent and a soft sponge and rinsed properly. Beer can and will create an almost invisible film of residuu ( at the bottm of the glass ) when left in the glass too long. Sometimes, even if you wash it, it will stil be there. I never pour beer in a dry glass. Any glass that I take out, is cleaned once more. I rinse it with cold water at least 5 times, inside and out, to make sure the glass is not even close to warm. Then I pour the beer.

 

Awesome advice above as per usual! Dude I'm just happy making a good tasting clean pilsner but I get your drift it didn't apeal in the head department and let's be honest who doesn't love some good head-retension! My best all Pilsner ah pilsner was brewed with just that but I recon a special type of pils floor malted bohimian pilsner malt by weyermann I scored a silver with it in my first comp. Recon mash schedule should help too. I recon if you brewed it again and gave the mash a nice long beta rest then up to 71c for 20 minutes you might get some dextrins out of that malt.

Another thought ever mixed half ale/half pils together I do all the time don't know if it yields better head but I'll keep believing it does.

Oh here's a burst carbed fresh light lager been in keg 3 days that beer was sitting for around 15 minutes for comparisons same. Only young but I'm happy with that.

 

For good head retention, as long as it's not necessary for the malt you're using, don't do a protein rest. Modern Pilsner malt is designed for single-infusion or step mashing. I like a step mash with two rests, 144 degrees F and 156 degrees F when using Weyermann or Avangard Pilsner. For the Blacklands Pilsner malt, it's the full monte: Glucan, protein, beta and alpha rests.