that's the purge valve for the EVAP system....so no that is not the regulator.
first thing i want to say is never, ever replace parts at random, on a hunch, etc. great way to waste a lot of your time and money. if that's your goal, then by all means go ahead. diagnosis should be carried out in a logical procedural manner to eliminate all possible causes until you find the root cause. it's about fixing it right the first time. plenty of members here can assist if you're not quite at that point yet.
there are many reasons why you might have a hesitation. most are pretty easy to fix - don't jump to fuel just because that's what you want to believe it is.
- start with ECU codes. even with no 'check engine' light, get a code scanner on it anyways to verify that nothing is stored in the computer.
- check your plugs and wires. i remember finding with my 1.6L accent that the plug gap was a bit too wide. i tightened up the gap a little bit and found a slight increase in engine responsiveness. i *think* it was 0.035" i went down to. it wasn't much below the stock value. keep in mind that this should not be done on platinum or iridium plugs. copper only.
- also note the condition of the plugs. if you have say a plug wet with fuel, oil or covered in soot that's a good indicator that something else is going on.
- air filter. see that it's not clogged or some other debris blocking the air intake.
- fuel is a possibility. i'd start with simply filling up at a different station. its not common, but it is possible to get 'bad gas' or at least cheaper crap.
- make sure all your other maintenance is up to date. oil changes, timing belt, etc. even making sure your accessory belts are tight is worth a look - slipping is lost energy.
- check for dragging brakes....you never know. a seized caliper could mean that the brakes aren't fully letting go of the disc.
there are other possibilities. these are just easy ones to check. give us more information, you really haven't provided anything so far. which engine do you have? what year is the car? what transmission? etc.
