few things that have me worried

[98Firebird]

1) car is heating up a little too fast and stays too hot just as of the last couple days. smells terrible after driving for a while too... i have a 160 degree thermo and manual fans, but it still heats up. this may be fixed by a flush, which ill do tomorrow

2) car idles at like 1100rpm and never less, why!?

3) oil pressure never passes 60... that normal?

4) i have an exhaust leak somewhere, which ill also check tomorrow, though im almost positive its at the back of the cat from when i hollowed it and had someone do a ****ty weld job. but the thing is, is it doesnt just sound airy, it sounds really really bad. almost like metal banging or something, its weird. should it sound like this?

5) gas mileage has gotten ****ty recently... what would cause this?

my mods that matter for consideration are:
msd coils
taylor wires
ngk plugs
headers
gutted 3" cat w/o2 sim
160 degree thermo
manual fan switch
all of which is fairly newer (1 year> )

[SilverBirdSeven]

A lot of times when a car idles too high it's because of a sticking throttle linkage, or just the idle speed isnt correct. This may also explain why the car heats up faster. Gas mileage could be any number of things. First things first, fuel injector cleaner.