Did you put the small washer behind the main jet when you put it back together? Is the TORS still hooked up? As mentioned in the 2 other posts, you are going to damage this thing running lean and with no filter.
I had a similar issue. I went a bought a junk harbor freight tester. I could only get 90psi out of it. I knew there was no way the was right. Borrowed a snap on from work and bingo. 180. Took that junk tester back and bought a craftsman.
I see mid 300's all the time with my trail tech computer. Piston, plug, and cylinder all look perfect and are inspected all the time. I basically keep an eye on it and use the temp as a input when deciding to re-jet based on ambient temp conditions.
It's all about transient fueling when changing between circuits. What is important is what state you are in when you make the transition. Lets say you are rich on the main. When you transition into the needle, being rich prior will affect how you set up the needle. Same goes on the opposite...