Right now - clean up - EVERY-FUCKING-THING - check the web and ditch EVERY listed chem in your house. Also ditch any solvents that have been used with the same. Ditch your vacuum pump if it has been used with illegal drugs - get rid of the fucking oil at least.
Prepare some crude dimethylamine (hexamine & HCl) - do it without a hood (it'll stink like fuck), but it has the same result in some of the presumptive tests as Methedrine and can seriously screw up their case. Leave it, non-worked up as a mixture - light yellowish muddy, where they will find it.
Remove and replace all light bulbs and any exposed copper in the house (if you have used anything which might make phosphine), alternatively try and make some aluminium phosphide (for purely non-illegal purposes)... Or even take the risk and try scrubbing it all off, maybe say you tried to use homemade phosphine to kill rats/mice in your house (yeah, you'd look dumb, you are guaranteed to look a whole lot dumber in an orange jumpsuit).
Extract some synephrine (from various sources) - allow it to evaporate slowly
Think about what evidence they will be looking for, what they will find and how to screw up their case
It is not illegal to extract non-prohibited substances or even be an amateur chemist doing things which leave similar (or even the same - particularly to presumptive testing) evidence trail.
Personally, and I am at odds with many when I say this (but SWIM is also free as a consequence, unlike some who followed their advice), make a point of being interviewed and ensure you mention the dialkylamine, the extraction of alkaloids (including n-methylphenethanolamines & caffeine - tell your counsel that, not them), that you use glassware for non-illegal purposes and amateur chemistry. THEN shut the fuck up and refuse to cooperate further.
This removes you from the witness chair at trial - all the evidence you need is introduced by them - you will not be cross-examined and your story - given it is given without restraint in a spirit of cooperation, etc. will be believable, not a self-serving, recent invention. Thus it provides the alternative hypothesis your counsel will need for trial without you giving evidence and being tripped up.
Also - make fucking certain you think of some alternative hypothesis (not for them - for your counsel) for any chemical purchases you've made - trust me, they will find them or know
Finally - format your computer - get one of the disk hashing downloads and hash your harddrive(s)
If you manage all that, and get back on here, be awful fucking careful posting (use a different name and just in case, get those on the boards you visit to change the username on any incriminating posts).
Don't put shit in storage - if you are under surveillance, they will watch you do so and know where to find it
Draw up a dairy - lab notebook - with innocuous lab notes going back some time