Adjusted timing- now issues starting and turning off

[Black70c10]

I've done some research on this but I thought I'd see what you guys thought. Long story short, bought a truck a few months back and it was running sluggish. So i checked the timing, and it had a base timing of 33 degrees.....seemed ridiculous so I confirmed TDC, then reduced the timing down to about 12 degrees BTDC. It seems to have a little more acceleration and less pinging. However, it now seems to struggle when I cold start and even more when it's hot.. you guys have any recommendations? I don't have any cam or compression ratio specs and I'm running mid grade gas. When it was at the original timing of 33, it fired right up when cold but always struggled when hot which is common when too at advanced I hear.

Also, when I shut the truck off, it sputters and acts like it wants to keep running for another second or two...what the heck is this about?

Anyways, thanks for the advice.