i've just fitted an HKS induction kit to my 93 WRX , however on fitting I accidently touched the wire mesh on the MAF housing so I cleaned it lightly with a dry cloth. Is there any chance of me damaging or contaminating the sensor, or is there a coating I've removed?? Also the car is quite hesitant on full throttle, and seemed to boost slightly lower(maybe just the warmer weather) do they have to re-adjust to such things???

 

Touching the wire mesh shouldn't be a problem, but hesitating under full throttle could possibly indicate lean(er) running, or just hot weather
The possible leaner running could be simply what the induction kit does, or it could be a damaged MAF. It would be handy to hear from someone with one of these kits at this point... The MAF on a 93 isn't that delicate though, I think
Look out for any idling problems as this is the clearest indicator of a possible/probable MAF problem.

 

I think the mesh you're talking about is just a disaster filter. It stops big chunks flying into the intake if the filter breaks up or is incorrectly fitted. The MAF sensor is a bit further along the intake than this.