What kinds of brews have you been making?? What's the aftertaste like? IF it's more acidic then it's your carbonation level you're pushing to the brews. I would use the two week 'set and forget' carbonation method for a few batches. You set the kegs to serving pressure, and temperature (get them to temperature first) for 2-3 weeks and then pull a pint. This helps to eliminate over carbonating issues caused by the rapid forced method.
Also, what are you using for water? If tap water, try filtered/spring water (like Poland Springs) for a few batches.
Racking to a second vessel for ales is pointless these days. It increases the risks of bad things happening (contamination, infection, oxidation, etc.). Better to leave it in primary until ready, then move to keg.
Kits are notorious for using ancient/dated methods for brewers.
Also, make sure you corny (not korny) kegs are clean and sanitized properly. What are you using for sanitizer?