Another neophyte chasing the Sour Gods

I have been baking sourdough for about 2 years now. When I first started, the bread had a nice strong sour flavour, enough for people to comment on how sour it was. Not sure at the time if it was to their taste, but it certainly was to mine. Fast forward to today, and my sour taste is nothing more than a memory. My recipe at the start was quite different to what it is now, and unfortunately I did not keep a diary or changes. Although in terms of the starter, things were not so different from today. From memory it was a 100% hydration with just plain flour, fed daily, left at room temperature. For the last 6 months or so, I have tried many variations, mostly from the posts of others on this website, all without sour success. This is what I have tried:  

1. Change the hydration. I have gone from 100% hydration down to about 50%. I gave this about a week for flavours to change;
2. Change the temperature. I have had the starter at room temperature (17 degrees), in a cold room (about 7 degrees), and in the fridge;
3. Change the feeding. I started feeding once per day, and have increased this to twice per day (when at room temp), presently the starter is in the fridge and I only feed when I make bread (every other day). On this day I keep the starter at room temperature for about 6 hours to reactivate after being in the fridge;
4. Changed the ingredients. I started with only ASDA bread flour, and have tried adding 20% Rye flour to the feeds;
5. Combining my existing starter and some Whole Foods starter;
6. Retard the finished dough in the fridge for an additional 24 hours.

 In some instances i have combined the changes above, but not always. For example I tried adding rye and refrigeration. The sour gods didn't hear my changes. My bread recipe is as follows: Start the Poolish in the morning, the day before the bake:   

• 140g Starter (This starter has a very strong smell, with hooch on top)
• 50g Rye
• 250g Strong bread flour
• 320g water

 Combine and cover with cling wrap for 24 hours (This used to be 12 hours, but I found that refrigerated starters take much longer before I see that point where the poolish collapses)  Morning of Bake:  

• 200g Strong bread flour (sometimes 150 with another 50 Rye)
• 11g salt
• 1/2 tablespoon malt barley

 Mix and knead for 10-20 minutes. Form into a boule, into the bannetton, let double in size and bake in a crock for 50 minutes.  I use this method because I am more than happy with the rise, the crumb, and the crust. It really does also taste pretty good, with the exception of the missing sour flavour which I still dream about... :-)   Are there any additional ideas I can try to get that sour taste back into my bread? I'm kind of exhausted for ideas.