maybe some water with a little methylated spirits added
that wouldnt have any nasty residues apart from the gunk you clean out.
I'm sure if woody filtered the cleaning fluid he got and let it dry on the filter paper - it might be only a gram or so - but obviously still has a significant impact.
or
injector gleaner maybe....???

Delivery.....if you didnt have a patient buddy...I was thinking of one of those pump up "weed killer spray bottles - they also come in the "improved backpack" version holding several quarts (liters) - but if using injector cleaner - probably the smaller the better.....you could set the car on idle...start the spray.....then go and sit in the car and rev 'er up - and do that for 5-10 minutes whilst ocassionaly giving the pump a few strokes.

Obviously after installing one of Woody's/Needswings oil catch can gismos - if you didnt have an oil catch can installed - it would just mean a 3 monthly clean rather than an annual one.

But...then ....some may be inclined this way - if you were familiar with doing it....how long would it actually take to clean as per a remove/replace - as part of a 10,000mile service? Maybe the same interval at which you change your air filters. The complication here (aluminium parts) is thread damage, gaskets etc.....and of course your time.

I must correct my original reference - you wouldnt obviously spray it into the Y-pipe, you'd spray it into the throttle body...