The FIA has moved to clarify the process by which manufacturers can modify their power units on reliability grounds.
Changes can be made on that basis without the use of tokens, and clearly the governing body has felt the need to make the process as open as possible – and at the same has tried to ensure that it has adequate time to deal with requests for changes, which at times been very last minute, by introducing a lead time of eight days.
A Technical Directive from Charlie Whiting said: “All requests for changes to the homologated power unit for the purpose of improving reliability should be made to me in writing with copies to the FIA F1 Engine distribution group. All such requests, with supporting data where necessary, should be made at least eight days before the modified power unit is first used at an Event and must include:
“1. A complete explanation of the failure, this should not only include clear photographic evidence but also when and where the failure(s) occurred.
“2. Part number references for both old and new parts.
“3. Full drawings of any new or modified components. Any pictorial or CAD views should be represented with the same zoom and angle.
“4. Test and investigation results supporting the request where applicable.
“5. Any relevant supporting information from external suppliers.”
Adam Cooper's F1 Blog 
It doesn’t seem like this will be hard to fake, along with a little assistance from complicit suppliers.
How exactly do they define a ‘reliability upgrade’ – I guess to prevent breakdowns but not adding any extra horsepower or changing the power delivery / drive-ability?
Must be a nightmare to police!