My first thought is the strings. But you may have a dodgy pickup.
On the tele (lefty) I am putting together (https://www.buildyourownguitar.com.a...ad.php?t=12407) I replaced all the electrics and got these pickups from Artist Guitars - https://www.artistguitars.com.au/buy...e-coil-pickups.
Have bolted it all together (photos coming soon) and I must say these pickups are far superior to the kit pickups.