Recently when ive been having trouble with my engine(3L vtec) shaking violently and has a hard time starting sometimes. My car shakes mostly when I accelerate followed by a flashing check engine light. It was first believed to be because of my EGR and after replacing that proved wrong. With some testing I found that my engine is misfiring in random pistons; then I discovered I had a faulty fuel injector. I replaced that and still has its condition has not changed. I was then suggested that i was having an electrical interference problem with things such as my ignition coil. Thinking back the problem may have started after I installed my radio receiver. I haven't checked yet but i may have possible soldered something wrong on accident (highly unlikely), or have wires crossing that shouldn't be.

Just let me know if their is anyway i can test to find out if their is an electrical interference or any ideas on what possibly could cause this. Thanks.