Sorry to repeat myself, but If you have never cleaned up the front engine block ground / main ground off the battery, do it! (And all the rest of course!)
On my truck the stud that holds the battery ground cable against the block wasn't very tight at all.
I am amazed at the difference it has made. The truck is running better than it has in many, many years. It starts from cold with about 1 - 1.5 turns, down from at least 3, and it starts when I touch the key when it is warm like it used to when I got it. Cold idle is a tiny bit lumpy, warm idle barely ever falters and if it does is barely noticeable. I'm barely touching the accelerator while driving and pretty sure I will be getting slightly better gas mileage.
I went to a distant Home Deport last night for some washers that weren't in stock at my local, got there 10 mins too late as they now close at 8PM. But I was enjoying driving the truck so much I carried on driving around, and then cruised the long way home. Dogs were with me and they like to drive around too.
It's a PIA in the ass to remove and replace if you have big hands and fat fingers like I do, but you could also loosen it and get a file in there to clean it all up a bit if you don't want to remove it. Which is how I think I might try the rear ground off the engine block to the frame etc. as there is such limited space.
Do it!