It does sound like you pcs is bad from what you are describing but you could also have some other problems which are causing low line pressure when hot. As far as having holding power in manual 1 here is why.... When you pull the shifter into manual 1 you have an additional band inside the transmission apply which gives more forward holding power ONLY in 1st and 2nd gear in each manual position, not in D or 3, and also the line pressure in 1st is upped dramatically by the pcm to not only keep this extra band applied but also because that band serves as engine braking for coast-down conditions such as going down a steep grade and letting the engine do the work instead of just your cars' brakes. When pulling down into manual 1 helps you take off from a stop then as a minimum you have a low pressure condition that is likely caused by more than just a faulty pressure control solenoid. Lubegaurd makes a great product but it isnt going to fix a poorly designed solenoid, which the only real fix is to replace it, but again that may not entirely fix your problem.
