Well I would start with the basics like a full tune up.....cap, rotor, wires, plugs, fuel filter, set timing, visual check of everything, clean grounds, run your codes, clean your MAF, new pcv valve and screen, new air filter, flush your brake fluid, check bushings, check brakes, rotate your exhaust bearings....
2016 VW GTI 2.0 Turbo
1989 Sonic Blue LX Coupe, 349 ci, TW heads, TFS Track Heat Intake, 75mm Accufab TB, 80mm ProM, 30 lb. inj, TKO, 3.73, 31 spline w/ TruTrac, MAC 1-5/8" LT headers w/ H pipe, Flowmaster, electric fan Moates QH
391 rwhp & 424 rwtq...Mustang Dyno 11.5@122mph