I didn't see a spring when I replaced the modulator but I did put the pin back in. There is supposed to be a way to adjust it with a screw driver, right?
spring may not have fell out but it needs to be there, mine had exactly same symptoms you are describing, i had let a quick oilchange place put new filter in to avoid getting dirty, trans was very slushy going home,ended up dropping pan and sure enough they were missing! got dirty anyway! lol
No amount of modulator adjustment will get rid of a 2-3 flare. Arbitrarily adjusting the modulator can hurt your C4.