David, it sounds like your SVT's gas regulator is just set low. Here's a photo showing where the gas regulator nut is located.
Note that the flats of the nut have the settings stamped on them. Mine was set to 1.2 in that photo. There are five settings in all.
This nut requires a special five-sided wrench to turn without damaging it, but if you're careful you can get by with a set of pliers.
I'd advise loosening the gas piston before adjusting the regulator if you don't have the right tool. I'd also highly advise buying a repro of the proper tool!
I won't leave you hanging at this point, I'll explain how to get at the gas piston. A loose gas piston can also cause inconsistent cycling. It will start out cycling fine and start to jam (typically a stovepipe jam) after twenty or so rounds, in my experience. This doesn't mean the gas setting is low, usually just the piston has worked itself loose because you didn't torque it tightly enough when you last cleaned it.
First and foremost - unload the rifle and lock the bolt to the rear.
Second, remove the cleaning rod.
Now locate the barrel band retainer spring on the underside of the foregrip:
Depress the spring and slide the band forward off the stock.
It's not necessary to completely remove the band, just side it up onto the barrel extension.
With the band removed, lift the upper heat shield at the rear and pull it backward to detach it from the lower heat shield. It helps to use a flat bladed screwdriver to push the gas piston backward as you do this. That will allow you to tilt the shield enough to slide it free.
With the upper heat shield removed you can remove the upper handguard. Simply slide it forward and lift it off.
With the handguard removed you can now access the gas piston system. All jokes aside, this is a short stroke piston.
Here is the relation of the gas piston cup to the gas block.
Simply pull back on the rod and it will side out of the back of the piston cup. Remove the rod and set it aside. Be careful not to lose the rear section or return spring as you remove it. These parts just slip together.
Now just pull off the piston cup and you've revealed the gas piston.
Note your gas regulator nut's setting before proceeding.
You can remove or tighten the piston with a box end wrench but the SVT tool has a notch that fits the square section. Remove your piston and ensure the passage is clean and free of oil and grease. With the piston out you can simply push on the regulator nut from the front and it will pop out of the back of the gas block. Ensure the ports are clear.
When you're satisfied install the gas nut at the next higher setting since you were complaining about cycling issues. Don't fret if you can't push it all the way back in place, the gas piston will shove it in place as you thread it in. Line up the notch on the gas block with the notch on the regulator nut for your chosen setting. Tighten the piston firmly and put it all back together!
Let us know how it works out.
And don't worry about writing in French for me - I'm English, just here on missionary work 
Kinda expensive at 60 dollars Canadian for a couple of little wrenches.
