Another decent meter that works well in the mobile is the radio shack SWR/power meters. If you have a Radio Shack near you, check for one there. They did keep a little stuff for radio in the one by me. And that is one item they do carry is the radio shack SWR/power meter. Also cheek eBay for them. They pop up sometimes. Though not a true PEP meter, they do work well for testing VSWR and also doing a check of the power, even if it's not true PEP power, I've found mine to be pretty close to a true PEP reading meter.
I know you said you think you have fixed the issue due to the warning not showing up. But that doesn't mean it's a whole lot better. May be just enough to make it work. You will be able to better tune it with a an SWR/power meter. No doubt about that in my mind.
In the end it's your choice, but I wouldn't trust my internal meter over an external one!! Especially if the radio has had work done to it. These are all JMHO's. Hope you get it all worked out.
And have a great day.
73 and God Bless
Sean