How do I see the coverage map for long Island?
There isn't particularly a map that shows what systems overlap Long Island, but you can go about it from the opposite direction. Determine what systems in CT and NJ you're seeing loaded, and search for them in the RR database.
For example, assuming one of the systems you're gettiing is the Connecticut State Police's Motorola system. Go into the system's entry in the DB, then hover on the little arrow beside each talkgroup listing. A yellow box will pop up with Talkgroup Category Menu on its title. Click on Talkgroup Category Details and you should get a map with a circle on it. That circle shows how far away the DB says you can hear that particular batch of talkgroups. When I picked the "Statewide" talkgroups - the first batch in the list - they show a radius of 60 miles from what looks like the center of CT, which also ends up covering almost all of Long Island right up to the city.
Unfortunately, in order to cover the whole of CT as it's supposed to, that batch of statewide talkgroups is going to have to cover some of NY as well. IMO it probably could stand to be shrunk down a little, but you're never going to get it to a point where you only get stuff from your own state and nothing else. The solution there is to set permanent avoids on the stuff you don't want to hear from out-of-state (probably easier to do it in Sentinel rather than doing it by hand on the keypad of the radio).