I want to replace the 99 Jetta engine with a square head. What kind of engine is suitable for transplanting to the old Jetta? I'm a rookie, don't laugh, thank you!

In this case, you must first find your substitute shop, and you must say. Their work and the serious mistakes of your vehicle have also led to serious consequences. Secondly, ask whether the valve replacement is a group or a single one. Your account may be because the valve clearance is too large, the intake valve and exhaust valve open late and close early, the exhaust valve opening is reduced and shortened, and the normal distribution is not clean due to insufficient intake air in the engine exhaust, which leads to the decline of engine power, and the various parts are affected by valve noise and wear increases. Or the valve clearance is too small, and the thermal expansion of the valve parts will cause the valve to close loosely or fail to close, resulting in air leakage, abnormal engine operation, power failure and serious combustion of the valve sealing surface. Jetta's speed dropped to 40km/h, 3-speed 2800rpm, 60km/h, 4-speed 2800rpm, 80km/h ... Because your condition is very serious, I suggest you go to the maintenance station for a comprehensive inspection of the engine system of the vehicle.