I am using a espresso machine and know that the current from the outlet is 208. The applicance requires a yp-19 15 amp 220 volts. The machine acts sluggish, and does not heat hot enough,, is there anything on the market (boster) to juice the machine 20 volts? I have used a transformer to 220 volts and it makes a big difference. The tag on the back states 240 volts

Your voltage is 208, not your current, which is rated in Amperes. Your statement-"requires a 220V"... and the tag on the back says 240V" 208 to 220 is 5%+, 208 to 240 is 10%+. Yes, anything that heats up will be slower on 208 than on 220 and certainly on 240V. Your wattage(heat) will be 10% less and therefore slower and not as hot. Transformers are available but probably not worth the cost to get a few more degrees in your espresso.