got a overheating issue

im just wondering if anyone has any input as to if there should be pressure in the coolant system on a 2002 chrysler pt cruiser touring? Also there is a slight gurgling sound sometimes when the engine shuts off, the temperature on the hand shows to be setting somewhere below the half mark most of the time, with a laptop and a elm 327 interface connected while driving it usually shows to be somewhere under 220 degrees farenheit. I believe a sticking thermostat was the initial problem, car got hot i changed the thermostat however also at that same time i changed out the ECU with a i assume remanufactured one i ordered from a company online. the new ECU was supposed to be plug and play since they had to have several different numbers to make the new ECU work with the old immobilizer. All that being said back to what ive done and what my present issue is. Other than the ECU and thermostat i have changed the water pump, the temp sending unit below the filler neck, the rad cap, tested the EGR valve, installed a aftermarket adjustable coolant temperature control unit, and tested the coolant fan.
the problem now is that as i said before the temp hand and the temp guage on the Laptop ODBll program says its not going over 220 degrees farenheit and there is a slight gurgling sound on the engine stops thats coming from the overflow box on the firewall near the windshield. should i be hearing this, is it over heating and the old ECU i reinstalled not reading the sensor correctly? I reinstalled the old ECU because with the new one i mentioned before it was reaching 250 degrees F with alot more gurgling and some steam. also again, i do know about these cars being notorious for insufficent cooling systems and i have replaced the cooland with the orange stuff thats supposed to be for all mixes in all vehicles. Sorry for the legnth of this, the mispellings and incorrect punctuation. thanks for any info.