I didn`t have much faith left in my fuel pressure gauge, so I ordered a new one, a liquid filled job, I installed it, and set the pressure at the regulator at 4 psi, I set the floats and idle mixture, it ran great, although i didn`t take it down the road, i came in to make some calls, let it cool off, then went outside to check it again, fired it up and let it idle, fuel pressure said 7 psi and it would barely idle, the fuel level in the bowl went to over the top of the glass site, so again, I set the pressure at 4 psi, reset the floats, reset the idle mixture, it ran great again, I took it down the road 2 miles, then came back, it ran fine, got in the driveway and the idle starts to flucuate, up and down, I get out and check the fuel pressure, it was at 2 psi, so again, I set it at 4, reset the floats, and reset the idle, what`s going on with this thing? I can`t get the fuel pressure to stabilize, and it`s causing all this havoc with idle mixture and float levels, it`s been going on a while now, and the new gauge brought to life what the problem was finally, but now I need to figure out how to get past it, I`m running a stock pump with return line, a holley regulator, and a demon carb. if it`s any help I have the carbon canister vapor line left open, should I seal it up so the tank can hold pressure? the gas tank used to always hold pressure, i installed a pump with no return line and the pressure was building up and overcoming the needle after I shut the car off resulting in a major flood. so I installed the pump with return line and left the vapor line open, is this the problem? when the car had the stock engine it always held pressure, do GM cars require this? it`s a 86 cutlass supreme. any help would be appreciated.