Hi there, it's good to see you getting to grips with the new toy.....
You might need new dampers but equally it could be wear and tear in the suspension components or simply that the car wheel alignment isn't set up properly. Because these are relatively light cars, getting the correct wheel alignment and even balancing the wheels becomes very important. But once set up properly it should be very stable, you shouldn't have to fight to keep it on a straight line.
First thing I would do is lift each corner and feel for play at the wheel, checking for suspension wear. In theory there should be very, very slight play at the front from the adjustable taper roller wheel bearings but nothing at the rear. At the front I find the upper ball joints and track rod ends last well, nylon bushes in the brass trunnions are a repalceable item and I recently had problems with the bushes in the dampers collapsing, poor quality replacement parts.
At the rear, with the driveshaft forming the upper link to the suspension you have 4x UJs plus rubber bushes in the lower links and holding the trailing arms to the chassis, loads being resolved through the gearbox & engine mounts, you have lots of places for slight wear which can add up to "too much", so be very critical in your assessments.
All good ? Then get the geometry checked against the workshop manual. You'll find that some owners prefer different settings, more or less rear toe with toe-in/toe-out or parallel wheels at the front, but for now set it as Lotus intended because that will work. Rear toe in is high compared with modern cars, if you take it to a shop for them to check make sure to take the manual settings with you.
Brian
Edit to add - beaten to it again !!!
