I have a Speakout 7-11 burner phone been using for years. Recently, I had to switch in my REAL phone SIM card to the burner phone for a few weeks. Will the burner phone have my real information tied in any way to the IMEI number?
If I install a new SIM card to the burner phone, will it be "clean" or is it best to buy a new phone and start over?
The phone itself would not have any information (as long as you're not saving any contacts and clear any call/text history).
However, the carrier would have some sort of record somewhere of the IMEI and the SIM card number that connected to the network.
When you install a new SIM card and activate/connect, the carrier would once again log what IMEI and SIM card is used. Obviously this information can be cross-referenced if the authorities decide to have a need for it and get the appropriate warrants, also gets a bit complicated if you used SIM cards from different carriers (Note that 7-11 Speakout uses Rogers, same as Roger/Fido/Chatr/Zoomer/Cityfone) but if they wanted to they can cross-reference the information.
So, depends on what you consider clean. There isn't really anything to worry about unless you are doing something to attract the heat.
In comparison, even if you brought a used phone on the market and used it innocently as a regular phone (no hobbying, just regular stuff, etc...), the IMEI of the phone could be tied to nefarious activities before. So, really, nothing is really clean unless you buy a new phone (and preferably an international phone (as carriers keep track of IMEI's of phones sold thru carriers (so they can be disabled/blacklisted in case of theft, non-payment, etc...)).