Q: Loss of horsepower and gas mileage

Hello. If timing is believed to be the issue, I suggest to not start the vehicle until the timing is properly set. If anything in the timing system itself is loose, it will cause the timing to become off. Off timing is unfortunately fatal for many engines, yours included. Think of it as a juggling act. The balls have to stay in a certain timed sequence for it all to work properly. If not, the balls will hit each other and fall out of place. Same thing with engine timing. The internal engine components have to stay in a similar timed sequence, if not, the components may hit each other and cause internal damage. If you need further assistance, I recommend you have a mechanic, like one from YourMechanic, inspect the power loss your vehicle is encountering and repair the issues.