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Hello there, on some vehicles once the battery is disconnected you can some times lose the basic ECU settings, if the battery has been disconnected for 20 to 30 mins or more, but this normally relates to vehicles that have the full multi point fuel injection system, where the injectors are linked directly in to the ECU as well as most of the other engine sensors, on these such vehicles you'd have to use a diagnostic scanner to remove any fault codes from the ECU memory chip, and drive the car for 30 to 40 mins so the ECU can collect fresh data from all engine sensors, and log all basic related settings back in it's memory. On some of the new vehicles this can happen if the battery is disconnected for long periods. But on your Corrado 2.0 16v as it's got the old style fuel metering head like on the later MK1 Golfs and MK2 Golf GTI, it's basically mechanical injection as it has the fuel distributor, fuel governor and air flow sensor all in the one metering head unit, so this set up doesn't really lose it's basic ECU settings unlike the more advanced ECU system like on most modern cars including the VR6 but as you've said it only took 5 mins to replace the battery you should be ok, from what you've said it does sound like one of the circuits has had a power surge or something for a split second, which can happen when you replace a battery. You should always remove the black negative (EARTH) lead first, and it should always be the last lead to fit back to the battery terminal. The red live (POWER) lead is always the second one to remove from the battery, and should be the first one to fit back to battery terminal before the earth lead. If you don't fit and remove the battery terminal leads as above then you can course a small power surge, or in some cases it can course a short, it can still happen if you do use the correct procedure but it's very rare. . Plus you've said that you have to apply full throttle to start your Corrado up from stone cold, this again is a classic symptom of over fueling. Full throttle down to assist starting is a symptom of a lack of fuel / too much fuel / very weak spark / very low compression. But like I say in your case as your Corrado starts fine when it's warm / hot, and is difficult to start from cold it'll be too much fuel meaning the fuel to air ratio, will be out so the engine will stall when cold or idle very lumpy until it's up to temp. It does sound as though the Coolant temp switch has died or is on the weak side, this can affect the car starting from cold or even when the engine is warm, it really depends on how the coolant temp switch has burnt out. They are normally white or blue in colour and have a 2 pin plug on the Corrado 2.0 16v The other thing it could be is the Lambda sensor, this detects any un-burnt fuel deposits with in exhaust waste fumes, but normally you'll have erratic idling and can have highish fuel economy complete with engine being under powered slightly, plus you might hear the odd popping sound from the exhaust tail pipe due to the extra fuel being used. These normally on the 2.0 16v have a black 4 pin plug with a separate earth wire. Most OEM Lambda's are Bosch ones, cost is around £58.00 to £78.00 off Ebay Some times the cold start injector can stick open which floods the cylinders with fuel, again coursing bad cold starting. This is normally linked into the coolant temp switch circuit, so once the engine warms up slightly the coolant temp switch, should then tell the ECU to turn off the cold start program. Secondhand these are around £25.00 to £38.00 off Ebay, and new from VW Main Dealer they could be close to £100.00 if not more, that's if they still stock them, if they don't then try VW Heritage. This is the part number for the 1.8 16v cold start valve ( 026 906 171A ) it might even be the same for the 2.0 16v. When testing the cold start valve / injector you can remove the 2 pin connector plug and see if it effects it's running on start up, or you can remove the cold start valve from out of the inlet manifold and see if it is switching off correctly, but if you do remove the cold start valve it could rip / damage the gasket. You can do a similar thing as above and remove the connector plug off the Lambda sensor or coolant temp switch, again just to see if it makes a difference or not to the engines cold start up. This is what some of the Forum members have done just to rule out each possible error from some of the sensors in question, that relate to this cold start up problem. When starting your Corrado 2.0 16v from cold it'll idle at around 1150 RPM for 3 to 5 mins in really cold winter weather, and around 1 to 2 mins in mild weather and even less in the summer weather. Once the cold start program has switched off, your engine should then idle at 850 RPM. I've got a spare coolant temp switch if you want it, it still works and has done around 75,000 miles. The part number is ( V026 906 161 ) this is a 2 pin and has a 10mm diameter thread with 1mm thread pitch complete with washer. I don't want any money for it you can have it F O C, if you want it and if that is the problem with your current one. Basically the same as this one on Ebay. http://www.ebay.co.uk/itm/261233673855?ru=http%3A%2F%2Fwww.ebay.co.uk%2Fsch%2Fi.html%3F_sacat%3D0%26_from%3DR40%26_nkw%3D261233673855%26_rdc%3D1 Hope this helps. Si