can you send a picture to were the op sender is?You have 3 options:
1) Underneath the intercooler,a brass, quarter-sized fitting, with a hex shape sunken head.... EXTREMELY difficult to get to - not recommended
2) an oil filter adapter plate - I've used 2 of them, Glow**** doesn't fit at all, greddy started leaking in under a month - not recommended.
3) The original oil sending unit, located right behind the alternator, slightly to the passenger side. Remove it and install the OP gauge. You will need to contact Autometer and get the adapter # (I forgot the #)... it's about $15.00, and any auto parts store can have it to you in 2 days.
NOTE: I did not get a CEL when I removed the original OP sender, but I'm also using a cobb accessport... I don't know if you will if you're not using an EM
Regardless, option 3 is your best, safest bet.